I say this because I just completed my first playthrough on normal difficulty and found the game to be comically easy if you focus on building up Yuela. Nothing can hit her... literally. I'm not sure if this is still true in NG+, as I haven't actually started a second playthrough yet, however I can say that she is certainly the most powerful character available if you're on your first playthrough.

As soon as you get the Beast Master armor, make her wear it and never ever take it off. Since it is the very first armor you get, it is relatively easy to enhance it completely, and it offers some of the best bonuses out of all of Yuela's armor choices. Compared to her other armors, it has above average speed and very good evasion, not to mention the inherent +1 Move and Burrow bonuses that come with it. When enhancing it, always choose +Str, +Evade, +Speed (later when her speed grows to a naturally high level, you can swap Speed for Luck), and equip any and all +Strength gems you find to the armor. It doesn't really matter whether you choose +Int or +Res. Int doesn't increase her damage since Yuela doesn't use magic (her sword dances are Str based), and she's not going to be getting hit by any attacks in the first place so Con doesn't really do anything. Try to finish enhancing the Beast Master armor as quickly as possible so you can gain access to Ferocity III, which greatly increases Yuela's damage output for a relatively low CP cost.

The Naqua Ninja Blade can be acquired as early as Chapter 5, and continues to be the most consistently reliable and effective weapon throughout the entirety of the game. The stats don't seem very impressive at all, until you realize that since the weapon applies Alert V to Yuela, simply wielding the weapon increases her evasion by a whopping 30 points. Even that alone would make it a fantastic weapon, but the Naqua Ninja Blade goes the extra mile and applies the Death effect to all of her attacks in addition to giving her a free Thief skillset (Lockpick + Search). The physical damage is somewhat lousy, however Yuela makes up for this with Ferocity, Flurry, and the vast array of sword dances that become available if you enhance her armors.

The basic Earth Sword Dance that the Beast Armor itself gives you usually does a satisfactory job at damaging enemies with high Physical resistance in the early game. Once you gain access to the Brave Lord armor, craft it immediately and enhance it three steps forward to unlock Dream Sever, a sword dance that does Omni damage for petty cost of 3 SP. This allows Yuela to essentially ignore resistances and damage types all together and engage any enemy in the game regardless of what weapon she is wielding. Do note that you can continue wearing the Beast Master armor while using Dream Sever, so continuing to enhance the Brave Lord armor past that is somewhat pointless. The only thing you'll get that's somewhat worth mentioning is Heavenly Phantasm, which is basically the same sword dance with three extra points of damage but costs 5 SP per use which is 66% more than Dream Sever. And it's expensive too, you only get it near the end of the Brave Lord armor's enhancement path. (EDIT: I forgot that the last upgrade for the Brave Lord armor gives you a high damage Omni combo attack, which is capable of doing very intense amounts of damage. You won't need that much damage until near the end of the game though, so it isn't a priority.)

If you use this combination of Beast Master + Naqua Ninja Blade, you can raise your evasion to an extraordinarily high amount at relatively low levels. By the time I finished Chapter 6, Yuela had an evasion of 80, which was technically 90 considering that I had Evasive II equipped. If you give Wil Battle Orders and place Yuela in an adjacent space, this is raised by an additional 10 for a total of 100 evasion, meaning that if the enemy does not have more than 100 Hit, they get a chance-to-hit of 1% and it becomes virtually impossible to hit Yuela. The majority of enemies in the game have a base Hit of 100, and of those that don't, a good number have less than 100. This means that Yuela is effectively untouchable by a vast majority of the enemies in the game.

By the time I finished my first playthrough, I was using Yuela + Wil for everything and I was clearing entire maps in only a few turns. I rarely bothered to use any other units for combat, as they weren't necessary. I had Yuela equipped with Evasion II, Ferocity III, Flurry II and Dream Sever, while Wil had Adventurer, Double Move, Battle Orders and High Rune. Wil did little more than scout ahead and move into a position where Yuela can attack the enemy with Wil's Battle Orders buff, while Yuela did pretty much everything else. Whenever I encountered an enemy with a very large amount of health, I temporarily swapped out Dream Sever for one of the Yuela + Wil combo attacks to achieve huge damage. I defeated the King Putetto in five turns with a level 50 Yuela, and the only time Yuela took damage was when one of her attacks got reflected. The only enemies I can recall that gave Yuela problems were the leveled Magmoles found in the Yuidora Mine near the end of the story, which were somehow very accurate and did very high damage to Yuela.

I really liked the gameplay at the start, but after Yuela got that Ninja Blade, everything became trivial. I'm planning on starting a NG+ playthrough, starting out fresh (only carrying over the synthesis rank) on hard difficulty, which will hopefully provide at least somewhat of a challenge. I just wanted to share what I've discovered about Yuela for anyone who was interested.

Yes. Yes, she is. And now you have posted a guide to make her even more so. Good job!
You can give yourself a handicap by putting her into the shop and leaving there forever.
On an unrelated note, there is no point in transferring craft level, it's trivial to get it back to max.

for me the most best character in this game is character that got skill blood suck III with adventurer..
well its sharty and lily..
skill blood suck III can make your character overwhelming no dying if you pro use that skill..
plus skill adventurer easy to complete map hunting material..
if use yuela always need change skill or accessories while harvest and excavation..
it make it slow to complete map and hunting item..
the best skill in this game is double action and blood suck for me..
so far skill blood suck got 4 character only can learn..
sharty and lily early can learn this skill while emelita need to get her last amor and fairy need to alchemy her most powerfull weapon..
i also always put yuela in party earlier playing this game , but in the end i not use yuela frequently and some map i not put yuela also in party coz many bonus character so damm powerfull and usefull then yuela ahaks!.

Bloodsuck is nice, being able to replenish your HP with every attack is very useful. However, not getting hit or taking any damage at all whatsoever is even better, which is something Yuela is very proficient at. Yuela simply doesn't need bloodsuck because she never takes any damage.

Also, the Naqua Ninja Blade gives Yuela the Thief skillset, which means she doesn't have to swap skills in order to pick locks or find secret passages. If you keep her next to Wil at all times to benefit from Battle Orders, then Wil will be there to mine any excavation points you come across. Harvest points don't require any skill to use and as consequence all units, including Yuela, are capable of using them. Really though, not having the ability to mine at all times isn't really a negative point for Yuela, since she can swiftly wipe the entire map clean of enemies, after which point you can come back to the level and harvest all the materials you need without having to fight anything by using deployment gates and Kohakuren's displace ability.

Now, I'm not saying that Sharty and Lily aren't useful, (Sharty's one of my favorite units), but at the end of the day, not getting hit > getting hit, and the ability to replenish health is irrelevant when you never take damage to begin with. You should give Yuela a serious try, upgrade her armors and focus on increasing her evasion. Her damage output is considerably high too if you build her right. By the time I finished my first playthrough, Yuela was consistently doing 50+ damage with each swing against most enemies (enough to kill all but the toughest enemies in a single turn), and she was only level 54. Her high speed ensures that she'll always get an extra attack, and if you give her Ferocity and Flurry, she'll carve her way through enemies with ease.

Really, the thing that makes Yuela so great is that you can send her into the center of a room filled with enemies and be confident that Yuela won't take any damage and every enemy will be dead by the next turn as they die trying to attack her.

i already finish this game more then 10 times ..i already in maps lvl 90 and 95.. if u use naqua ninja blade in that map i think mops take little damage only.. yuela most powerfull weapon kitchen knife and got skill fine chop in that sword.. i tell u la.. event your stat con,str,int,rest,speed, all maximum its still pain when monster attack your yuela at map lvl 90 ~ 95.. mostly skill flash step evensive and counter attack not effective at map lvl 90~95. but still.. yuela is main heroine.. if u can make its hp max 500hp.. by use stone +hp or fountain of young for reincarnation level .. now it's really overwhelming.. but to reach that points.. its really hard..

Well, I was referring to the "normal" game, not NG+. As far as I know, the highest level dungeon in a first playthrough is the level 70 Deadbeat God map, which Yuela is capable of easily beating.

Do monsters gain lots of Hit bonuses in NG+ that they don't have in normal NG? If so, I can see how Yuela wouldn't be as effective there. However, if their Hit stats remain mostly the same, then I don't see how Yuela would be any less effective in NG+ than she is by default. The Yuela I described in my original post doesn't use Flash Step or Counterattack, since those are very unnecessary whenever you have an evasion of 100 and nothing can hit you in the first place. Likewise, if your evasion is at 100, it doesn't matter what level your Str, Int, Con, Res, or Speed is, since nothing can hit you the game is still easy either way.

yeah you right.. yuela is best option for new game..