Atelier Iris 3 Tiers:
Top Tier:
Iris
Normal Edge
Plua Edge
Normal Nell
Middle Tier:
Everything else except
Bottom Tier:
Jiptus Edge
Faustus Nell
Diemia Nell
As for my rationale, I personally believe that the best way to handle combat is to fill the burst gauge early and keep it from draining as long as possible. The non-mana party, I believe, is the best at doing this. Note that having low speed vs average speed is much more detrimental than average speed vs high speed.
Iris doesn’t inflict a lot of damage without burning a decent amount of skill gauge, but Mana Storm basically handles almost all non-boss monsters throughout the entire game. Anything it doesn’t kill suffers knockback, so it’ll probably die before it’s turn comes up. Elemental conversion gives you the money you need early in the game, and Luplus summon is quite possibly the best spell in the entire game.
Normal Edge has both Windmill and Cross Rain to keep the burst gauge from draining and since this form’s ultimate weapon has 7 hits on it, you don’t need to waste one of his three attributes on hit plus, but can use it for quick and blessed weapon or attack [L] instead.
Plua Edge has a wider array of attacks than Normal Edge, but lacks in damage just a little bit. However, a bursted Blink x3, Illusion Edge combo does significant damage to any enemy until the middle of the game. Illusion Edge also does lots of hits, so this form isn’t too much of a drain on the burst meter.
Normal Nell has a nice array of skills even if she doesn’t have good AoE skills. Break Slash is one of the better skills in the game as it knocks back for only 1 skill charge and still hits 3 times. Eins Zecksclaw is a decent attack versus 1 enemy that does a good number of hits and damage.
As for the bottom tier, Juptus Edge and Diemia Nell are just too slow and inflict too few hits to be good. Faustus Nell blows because she is supposed to be a hybrid character, but her ultimate weapon sucks at magic and her skills are all magic based. Faustus Nell is also slow as tar.