I am also a fan of using lots of low level mosters.  I keep track at how much damage people do, then select monsters that would go down in 1-3 hits.  You have to kill more of them to get the same experience, but the battles are shorter so it works out about the same.  
Of course, I'm also a fan of using minions.   But I generally only use minions when the monster is traditionally something you can drop in one hit.  Low level cultists, kobolds, skeletons, goblins etc.   I would never make an ogre or or an aberration a minion for example, because they have traditionally been thought of as tough or exotic.    I also ensure that the players know that the minions aren't going to be much of a challenge based on descriptions of their demeanor, equipment, etc.  Nothing pisses off a player more than using a daily power on a minion.
Since the minions are just meant to bulk up the fight and give you easy foes to trash, I don't really have a problem with automatic damage cleaving through them quickly.   I also don't have a problem with them being expendable or useless.  
What I do have a problem with though is tracking hit points for creatures that usually go down in one hit.