Companions auto level when you re-recuit them to your EXACT xp level. Even if it's not a full level over where they are they are instantly granted that much xp. Henchmen however (as purchased in the hall) gain no bonuses whatsoever, even going so far as to get the exact same amount of exp you get when fighting enemies who are much higher level than they are.
There is a bug however, that a companion/henchmen who is not in your active party will lose a large portion of his or her inventory. DO NOT store excess items on unused companions, and it would be wise to completely strip them of everything but their current equipment before dismissing them.
As far as a balanced party, I used double-warrior mage archer myself. I find that rogues are simply "less good warriors". In classic you can get away with nearly anything and if you can survive cyseal in tactician you are probably good for the rest of the game continuing on the same way.
Last edited by Sotanaht; 07/11/15 11:52 PM.
