I started doing heroics yesterday.
Had the same problem during the first 5 minutes.

Then I figured that I had to just lower the healing shaman spell throttling by one cast. Usually my healing shaman heal macto was LHW,,, I just removed one coma ( , ) and that fixed it.
Ocassionally I have to hit riptide on difficult pulls, but that's very rare.

Make sure you have your Holy shield always up on the pala.

I run a tankadin + 3 DPS + dedicated healer.
My usual pre fight buffs are the earth totems for strength and armor + earth shield on the pala. Then he pulls the mobs. If there are 4 or more mobs I toss also riptide on him before he pulls.

The main problem I saw is that my pala has tho handle the initial onslaught after pulling during the first 4 seconds of the fight when all the mobs start hammering him and the first heal has still not arrived. After these first 4 -5 seconds he tends to stay almost always at full HP.

My totems / blessings is the following:

Pala --> blessing of sanctuary + seal of light. Judgement of light is in the tanking rotation. You may be surprised how much extra Hp does seal of light + constant judgement of light generate. Also retribution aura is used, except on some boss fights where shadow resist aura does good, like ingvar in UK.
Shamans --> Water shield + mana totems. I know that most people prefer to use healing totems, but as long as my healer has mana the pala is practically unkillable, so for me mana = more healing to the pala = everyone else lives.

What did I accomplish so far?
Heroic Utgarde Keep --> cleared
Heroic Grundrak --> killed the mamooth boss. Tried the heroic only boss too, but he wiped me after enraging, so he is not an option for now.
Heroic Hals Of Lightning --> First two bosses with their respective achievements. I did this run only for these bosses achievements. (Lightning stuck and shatter resistant ones). Wanted to make these achievements before getting good gear because most people just say there are impossible with my crappy gear... they were wrong

Naxx 10... Yes, naxx 10 --> reached Patchwerk with only my 5 toons. The ooze room was pure pain to bypass, but I found that sacrificing my earh elementals and my pala at the end I could just run past them and then divine intervention or sacrifice... (the spell that kills tha pala and removes a party member from combat). Patchwerk oneshoted me and I didn't try again because it was just a test run.
On this one had to remove another coma from my healer healing macro to ensure that he spams healing all the time. Had to wait for mana recovery after every fight, but didn't die after a bad pull that pulled 4 of the mini-patchwerk golems in the room before the oozes.


So, basically, with the same (or worse) gear and my shamans severely undergeared I just had to force more healing spam on the tank to be viable in heroics. Of course, a bad pull and usually it's a wipe, but that's what heroics are for

This is my tankadin:
http://eu.wowarmory.com/character-sh...er&n=Loladinus

This is my healer:
http://eu.wowarmory.com/character-sh...usher&n=Tuljin

These are my DPSers (note the crappy gear):
http://eu.wowarmory.com/character-sh...usher&n=Buljin
http://eu.wowarmory.com/character-sh...usher&n=Nuljin
http://eu.wowarmory.com/character-sh...usher&n=Ruljin

I have an offheal macro on the DPSers that cast chain heal on themselves. This usually makes fights like Ingvar in UK very easy becayse then shamans drop on HP after the shouts I just hit that macro and they heal themselves to full HP again. the healer takes the residual heal from the 3 x chain heal and never stops healing the tank. He only casts LHW in instances and ocassional riptides... nothing else.

Once I get properly geared I will probably switch the healing shaman to DPS too, but for now it's just not a viable option.

I used Thrym in Zul Darak (the 650k HP elite) to tune my macros when I was lvl 75. At lvl 80 he is still a viable target dummy, but he goes down too fast and doesn't give enough punch to compare different setups unless your tank is half naked.