I think it really was mainly the cleric's fault. The tank was really concentrating and didn't slack, but he was using a non-enhanced sword so I guess it was hard to keep aggro sometimes.
And there are good clerics too XD I've been in a party where it was me, an archer, and two other mages with a cleric. We got rid of the entire room and was running around for more. I didn't use a lot of stones or pots either (but then again, I wasn't tank LOL. Our tank was a kick-ass mage running around with 3.5k HP at 5x @_@)
But it was just really annoying to know that there ARE good clerics and there are clerics who slack off - AND have the breath to complain about other people.
EDIT
@ Ralath
Most of the tanks I've partied with are quick to notice that my HP is rapidly bouncing and try to save me before I kiss the ground XD I rarely use NP on my archer.