Why do I hate thee... let me count the ways. It takes five hours to clear you. You only have two bosses to give me Badges of Justice. You have too many trash mobs.
Ok, it wasn't that awful. But it really did take five hours, including the begging to get people to come help us poor druids out. And swapping members multiple times. And dying so much that we had to repair at least three times each. But other than that it was great! (Cough Cough). Realistically, it was probably that way because none of us had done Heroic Sethekk before. And most of us hadn't really done regular Sethekk all that much, for the reasons listed above. Most people don't like this instance, so by all means torture the druids by sticking their epic boss in there.
So the biggest thing I can tell you is take two healers. DPS is not a huge concern here, but healing is. We started out with three DPSers (shammy/mage/lock and then lock/mage/lock) and wiped alot. After we swapped out the extra lock for a priest, we had a lot less trouble wiping on trash. We still wiped on boss fights of course :) Crowd control is pretty important in here. Luckily our warlocks were able to use banish/seduce and we had a mage for sheeping. We also had the priest use shackle for the occasional undead caster.
I'm not going to run down all the strats for Sethekk, surely you can check the Wiki for that. But I will tell you how the Druid boss worked out for us. First of all, we decided to use the kiting strategy. Mostly because we didn't want to impose on our buddies who had given up their evening to come with us any more than necessary. There was some concern that we needed to clear Ikiss first, but I can confirm that this is not necessary. Simply pull the boss backwards into a room you've already cleared.
After you click the totem and "summon" the boss, it takes him a minute to do his thing and fully spawn. This gives your tank time to HoT himself (you did bring a druid tank, right?) and get some range on the boss. Then the tank just pulls it and runs out of the room and back to wherever the group is waiting, he shouldn't take any damage while running. Once the tank arrives the healers focus on keeping the tank up with occasional HoTs getting tossed to the DPS folks.
The druid boss will cyclone and daze people, which doesn't really do a lot of damage but takes them out of the fight for a few seconds. This is why backup healing is needed :) He can also charge at people, this seems to be the person standing farthest away. So task someone with being the target who can take a bit of damage (1-2k hit). We had the warlock do it since he had a pet to help him and could drain life to kick his health back up without a healer wasting mana. He also has a caster debuff he does, when a caster gets it they need to stop casting or their mana will be drained.
The bad part about kiting Anzu out of the room is that you don't get the bird guardians to help you. The good part is that you really don't need them since you won't be dealing with the adds that Anzu summons. So this becomes more of a tank and spank fight since no one has to deal with killing extra mobs.
Another thing that really helps in this fight is that at 66% and 33% Anzu will banish himself for about a minute. So this gives everyone a chance to bandage, quaff a mana pot, rebirth anyone who might be down or innervate a healer who's low on mana. We found this was a big help in getting through the fight, although we didn't take very good advantage of it initially. We didn't kill Anzu on the first try, mostly because we didn't know what to expect. But we took him down fairly easily on the second try, and I'm quite proud of us for that!
One thing to note here, Blizzard is planning to prevent the use of this kiting method in the next patch. They actually have patch notes to this effect on the PTR, so if you want to use the kiting strat I suggest you get it done pronto. I have no idea when this 2.1.2 patch is planned to go online but since it consists primarily of bug fixes, it's a good guess that they will push it out the door asap!