The Chosen Ones

Occasionally Useless :
Illusory Double, damage is okay but not beefy enough to survive most elite/epic bosses
Seal of Ressurection, useful only in early chapters. In late game it's a lifesaver if you have glass cannon Fradz.

Near Useless :
Spinning death, in late game where you have 5 siphon health and godly items using this ability actually lowers your DPS :/
Sword Dance, can't move for 5 seconds + boss special attack = GG
Mesmerizing Ice Crystal, sometimes the taunt ability doesn't work

Totally Useless
Note : Actually not a single ability in this game is totally useless if not because of the fact that some ability is totally inferior to another to the point of one can't think of a reason to pick the other
Headbutt, inferior to Impact Flare. The health cost is even making it worse.
Double wave, inferior to Discharge