[Rockabye]

As much as I wanted to click Evoker just for the sheer straight-forwardness of it... no, Engineer. You're probably relying on your bots to do most of the work for you, you can't really control them in any special way, and unlike Summoner you're not gaining any skills from them to use yourself, so you're looking at a really passive playstyle of using up your momentum trying to maintain them (which isn't very fun). Of course, this opinion is entirely based on how Engineer functions alone, and not necessarily any potential multi-classes you could make with it.