Try out the divine disciple tree for the SLAs, but be sure to pick up maximize and empower first, there is no added cost with these on the way up. I have my own divine disciple and love it, especially out in desecrated temple of vol. Won't have all the fancy bursts and such for healing, but if something is already dead before it hits you do you need the healing?
A second option would be the defensive tree, at tier 5 it gives a permanent blur, and adds the spell into the cleric book at level 3 i think. Great if you don't have a wizard/bard/sorc to pass out blur. Various stuff in the tree will boost hitpoints and armor class, making the cleric more durable when in there swinging the greataxe. Not tried one myself (i did try a mix of one with 6 cleric and 6 paladin but did not run a lot of quests), but it should be pretty tough and need less healing. I'd think grab empower heal then whatever other feats you wanted.