Your DPS Willyrs seems low. I know that you probably can kill it with the amount of DPS you have, but it will be tougher. I switched our balance for warrior last night as we got a kill. Balande druid was just doing horrible DPS. You do have pretty decent healing setup, not so good for interrupters though.
For reference, this was our DPS when we had the boomkin -
http://www.worldoflogs.com/reports/8...?s=3425&e=3746
And after we switched him to our fury warrior -
http://www.worldoflogs.com/reports/8...?s=6124&e=6582 - and the DPS improved.
This is our kill DPS -
http://www.worldoflogs.com/reports/8...?s=8993&e=9704 , but bear in mind that Horridon takes 200% extra damage, so the number are bigger.
But what truly worked for us (and by no means we executed the fight perfectly) is the following.
Tanked Horridon near the doors, but not too close. Swapped tanked after every door. Since you have to palas (tank and holy), you can drop the triple puncionation stack by using the full dmg immunity bubble (the one that drops aggro as well, I'm sorry, can't remember the name) and have just one tank mainly on Horridon, if one of your tanks is better for the adds.
When the dinomancer comes, focus on him, bring him to 50%, have one deticated orb clicker and smash him into the door ASAP. You DON'T have to kill mancer to get the orb, at 50% of his health the orb will drop.
Make bloody sure that your healers see the disease and poison stacks. If their unitframe add-on fails at that, have them keep blizzards raid frames, that shows the correct amount of stacks.
Have your hunters MD tanks the runaway adds.
Door 1 - had the rogue/hunter of ours MD the adds to me (guardian) when they were running amoc. Knocback, roots, the works on the small ones. Interrupted the basilisks as much as possible. Yelled out when someone (me) was stoned to get dispel in as fast as possible. Stacked the mobs up and burned them down. Ofc moving from sand traps is very important. Have your druid pick up ursual vortex and typhoon. Use those for the small adds. Work wonders. Ofc putting symbiosis on one of the hunters helps as well (he gets the frost trap for slow from a hunter). Try to kill the adds as fast as possible. Use mass dispel from the priest to get rid of the stuns on melee.
Door 2 - we premarked 2 of the priests on the side (the ones which come down together). That enable us to pre-assign interrupters for the poison bolt cast. We had warrior and rogue for that. But for you, you should have shaman on one of the priest as it's dedicated interrupter and the rest of your DPS who have long CD should focus on interrupting the other one. You will get lot poison through, but just dispel the tanks and people with high stacks first. The interrupt CD on your hunters and priest should be enough to keep rotating interrupts. Your add tank can help to interrupt as well, but don't count on it too much, as most probably he is targeting someone else.
Door 3 - the crappiest for us. Have your healers (you have a very good setup - pala, priest and mw) dispel the person with highest stacks first. Your prot pala should be able to dispel himself, so dw about him. Only thing really tankable is the Warlord, the rest just fixiate on someone and start putting diseases up on the fixiated person. Move the warlords from the orbs, make sure the DPS moves with the tank as well. Orbs move in a random direction and will firstly spawn under the warlord which is casting the orb. What truly helped us, was to put more focus on the smaller adds to get them down as fast as possible to lessen the disease, as we had only druid with symbiosis from pala, dispelling people. Pala tanked helped out as well.
Door 4 - stack everything up, have hunters MD the runaway adds to add tank. Again we focused down the flame casters, lessened the raid damage that way. And tried to AoE the bears down so we could get the trolls down at the same time as well. What we found out was that if we left the bears later, once most of the caters were out, we had only few totems up.
Once the Wargod came down, we focused on him, killed him before my stack of puncture run out. After which our pala bubbled me, I lost the stacks and took Horridon. By killing Wargod and leaving Horridon, the dino starts hitting 100% harder with all his attacks, so tankswap when other tanks needs to loose stacks or needs some healing.