Dungeon mechanics I'd like to see

[CYoung187]

I'd like to see a boss that similar to ultimecia in ff8 would randomly disable an ability/spell from a player. Guess what you don't have this ability this fight, find a way to adjust.

[Feilina]

They could dig out the system we had in 1.x, the ability to break horns, disable arms or simply razor the head of a doblyn.

Ex:
Left arm has been disabled -> cleave does x% less dmg for y amount of time
Legs disabled -> no stomping
Head shaved -> no more PbAoE

[TouchandFeel]

Just off the cuff, I think it would be neat to see some Multi-npc (not adds) boss fights.
As an example, you have a fight with three different boss NPC's, each with their own flavor/schtick, and the trick to the fight is to use their abilities against each other such as one boss will do a telegraphed aoe at their targets position so you have to position that are on another of the bosses so that it then brings down their defenses and opens them up for attack.

Really there are a lot of potentially cool mechanics for such a setup and I feel it should definitely be explored.
Fingers crossed to see the Magus Sisters as a future boss fight
http://finalfantasy.wikia.com/wiki/Magus_Sisters