Illusion works just fine, right up to the highest levels, if you just invest the perks in it - which seems like a reasonable requirement for a character who specialises in that. Frenzy plus dual cast plus relevant perks - affects targets well over level 50. Without potions.
Maybe the frustration stems from the non-inclusion of Dominate spells in the master level. I do not need a ritual speed AoE calm/frenzy/fear. I want a (permanent) non undead thrall.
Until further notice 21st of October, please DM me for important stuff, and let the game master control my characters