What if you made the "pets" more feral and uncontrollable, but also more temporary and expendable? More like how they are in Diablo II?

Like a spell that summons a Skeleton to jump out of the ground and attack the target. Each attack it lands decreases the skeletons health. When the skeleton dies, it explodes, doing Extra Damage to the target. Different Rituals pop out a different minion which have different effects.

Since the "summons" are not controlled by you directly, you can also have multiple minions out and running around the field at a time since you don't actually control them.

Of course, you'd have to maintain your assault, so I'd go with a LifeTap (HP converted to MP) and a minion that drains the HP of a target as it attacks and feeds it back to you.

Just a thought.