Try get some logs, I initially thought this was about heroic garrosh, as for normal I don't see the value in solo healing it and I would probably say it would be easier for a druid/shaman to solo heal it than a disc. (Gear dependent) Shelling the whirls is a bonus and isn't needed to survive on normal, are you stacking under the boss or staying ranged? The latter would be easier. You should have enough raid cd's for the whirls. Also, they should be smite spamming mostly, except during whirls I guess!
I run normal Garrosh with 2 10-man groups. One killed it and the other group didn't (the one which initially had pala/disc as healers (not an healing issue)) due to DPS/tanking issues (but not that important anyway now).
We are not stacking under the boss, people are staying ranged for Whirls/Weapons (melee stay only at melee during whirls if they have their own CDs). But it generally comes down to how much damage people take from various things and how good the DPS is on boss (clearly seen from 2 groups (1 with the kill and other with no kill) with roughly the same ilvl, but different players).
In either case I got my answer what I needed for next reset, thanks for the discussion. Good to know that pala is a decent healer for this fight. I just though that pala's mastery is shields and disc does shields (and the absorb as I've been told kinda goes to a certain amount only) so that's why the stupid question.