The build andhow you handle healing is a big thing tank and healing build both have to be right on. If your having issues @ 20 in IT somthing is prolly off. Warden at lower levels is really strong with two hots and at 20 you may have 3 put that with a heal from sentinal you got a good healing ofcourse u will be spam healing and over healing a lot but that's the nature of the beast. Also you may want to drop the cleric dps and bring in a 2nd mage that could be chloro/archon to bring some nice support and dps boost. I run warrior tank reaver/paladin/warlord with most points in paladin I find for lvling the aoe dots with the midigation from paladin makes for a good tank build. Warden sentinal is a good combo for a cleric healer, mage pretty much stormcaller/ele or ele/stormcaller would be the easiest to box aoe and single target, ranger/marks/assasin or a sab build for your rogue, that leaves you a support character bards are ok but I think. Archon/chloro is a great and better support then a bard. Just my 2 cents.