That's what minions are for.

I haven't found that monsters have too many hit points at all. In fact, it's refreshing that monsters can actually take an action or two before being mowed down. Every monster is an interesting component to the fight, and every fight is a challenge, not just a tiny hit to your daily resources. It's not an expendature of 20-25% of your hit points and spells, but rather a much larger percentage of your encounter cababilities (hit points, action points, and encounter powers), and a smaller usage of daily capabilities (daily powers and healing surges).

You may be finding this because at the end of a fight, the party is beat up and mostly out of encounter powers. But that's normal. That's why they have healing surges, and only need 5 mintues to get their encounter powers back.