To be honest, the first time I play the game, I just used my creature 2 or 3 times a short time, that's all! Maybe if I play on harder difficulty I use my creature more times?
And what about the XP-points? Have someone any idea if my creature kills enemies, goes this XP for killing a enemy to my hero or not?
XP is all yours. The only time I have found experience vanish is when you charm an enemy and they die while they're your pet, you do not get XP.