I run a mixed group (pally/priest/boomkin/shaman/mage) and after banging my head against normal mode a lot I switched out the boomkin for a 2nd shaman and TOC got a lot easier. I added Grounding Totem to the end of my shaman DPS macro so its pretty much always being put down and I worked a lot on my Paletress fight on Normal. Finally tried Heroic over the weekend and actually did it on the first try, though my Pally was the only man standing on BK phase 3.

There's a few key points you need to master to make this instance doable:

1) Learn the jousting approach. You should get to the point on normal where this is easy, then the heroic guys just have more hitpoints.
2) If you roll the rogue then make sure you drop your Cleansing Totem(s) and move out of the poison cloud. If you roll the shaman try to interrupt his heals as much as possible. Using Grounding Totems really helps during this phase if you roll the mage
3) Get good with the cleanse on Eadric. Also either turn your guys or master the "interact with target" technique. The key on heroic is to get your DPS back on track as quickly as possible
4) On Paletress again make sure that you have your post-fear scramble technique solid. Don't bother going to heroic until you can reorient your team quickly after the fear. Once this is second-nature, heroic gets a heck of a lot easier. If you have a Shaman you MUST purge the Renew off the summoned mob. Make sure you are putting down Grounding Totems. If you do all these things then this fight will seem a lot less like a crisis and more like a tank n spank. Once I was putting down 2 totems reliably and re-orienting my guys reliably, this fight became substantially easier.
5) BK phase 1 is a gimme. No tricks here. Just make sure you have a Cleanse totem down
6) BK phase 2, try to DPS down the adds but you're going to take a ton of damage on your tank so this is a healing intensive fight. As soon as the BK is dead auto-follow your guys to get them away from the remaining ghouls and then you'll be standing on top of each other (preferable) for Phase 3. Make sure your reset your totem farm because the ghouls kill them.
7) BK phase 3. AOE heal while DPSing as much as possible. I usually pop Divine Sacrifice on my Pally just to help smooth out the damage. If you lose a guy or two don't panic, just keep at it.