Ran regular a few times today, 1-shot everything, finally got the trinket for my DK tank, then ran heroic. died once on black knight then killed it second time. This time I subbed in my holy priest for my mage, so it was DK+priest+3 shamans. It actually felt a lot smoother/easier than DK+4 dps, as I almost never had to cast heals on my shamans so they could DPS nonstop.

Couple things, as noted above, that make things a lot easier:

1. Run out after you dismount the 3 champions, you have as much time as you want then to setup for ground fighting.

2. Eadric is a pushover, just tank'n'spank and turn around when he radiates. The chick is a LOT harder imo, what I do is drag my team over to a wall and park them there, I tank her a bit out (she doesn't run far so range becomes an issue). Have click-to-move enabled and interact with target set to a key, so after fears you can interact to face the right way and then stop move key. This is a very dicey fight, keep the tank full always since the 2 guys can whale away on your tank when feared (so unfair!). Priest is nice, since I can fearward the tank and also do some quick group heals.

3. For black knight, mesh's suggestions worked great. I dont' even bother popping out earth elementals or army of the dead in p2, I just put my guys against the wall, drop totems, REDROP GROUNDING TOTEMS EVERY 30 SECONDS, and just beat the crap out of him. One really important thing, remove the thunderstorm minor glyph that removes the knockback component! It really, really helps out a lot if you drop magma totems, and when adds are near 30% knock them back and do a tstorm to kill em/ get em away. Also its critical to ALWAYS have grounding totems down. Having a dedicated healer makes this easier, since my DPS can just go all out while I spam prayer of healing on my priest. I tried first time with my resto druid, and it didn't work at all, since resto druids don't really have a good AOE spammable heal spell (Wild Growth is on 6 sec c/d).

The key to Black Knight is having a clean p2 where everyone comes out alive and full hp. If you can manage that and not get flustered, you can burn through p3 quickly.