I struggled as well, like you mention, particularly on the early 30s. Gear helps a lot on this, as do a few more levels and ranks on healing spells. I started going deep Disc and it was awful, as soon as I went deep Holy for the +healing from Spirit it was night and day.

I tried Hellfire at 30 and decided my team was not ready for it. Switched back to Rain of Fire macro and it went smooth again until I got to 32. Truth is you are on a bad level range to fast level, so take your time clearing GY to farm the offhand for your 4 casters and start doing bigger pulls at 34. Once you can reliably clear Library, farm that for the dagger. Having a little bit of +healing made a really good difference for me.

Do not worry about XP/HR before you have mastered safety and reliability. A good geared warrior can hold mobs much longer before the aoe starts, which means your party dont take melee damage, drastically improving your pace.