OK, so I've been slaving away trying to get my Balance, Death and Ice grandmasters through Celestia and WinterTusk. MANY, MANY times I have had to use henchmen.
Problem is, the level 60 henchmen use low-level spells (Storm Shark, Phoenix) and do very stupid things - like cast their school blade on someone else, use a wand with their blade, and then use wands whenever they have nothing else to play (really messes with my ability to feint!!!). I have NEVER seen a level 60 henchman use a level 58 spell...like Leviathan, Forest Lord, etc. AND I have never seen a level 60 Life use Rebirth.
They are not the brightest wizards around, that is for sure. I don't use henchmen often but I accept them for what they are. I suppose if they waited for pips to cast high level spells then people might complain that the wizards don't do enough to help or just pass turns too much. IMO they do a good job of creating a distraction and absorbing the attacks from the monsters so that is what I usually expect of them.
True, Life wizards are the most useful, but when you're balance against balance or death against the EVER-SHIELDING life mobs OR anything facing ice/tower shield mobs, an elemental sure comes in handy.