To that end, I would suggest getting rid of the defense enchants (including the shoulder one) for more stam and armor. Maybe if you don't need the threat from Armsman you could replace your glove enchant with 240 armor.
I'd also try speccing into Will of the Necropolis, especially since it's going to get buffed in the new minipatch (no more cooldown).
You don't mention what situations or fights you are particularly hard to heal on. If you're consistantly harder to heal than your pally or bear co-tank, perhaps it's a matter of gear. If it's certain fights, perhaps you are mistiming your cooldowns. Etc etc.