I don't think gear is their issue. I looked at the mage and one hunter and the mage is 516 with the hunter right there at 514. Unless the rest of the raid is FAR behind those two it's not gear but execution that's the issue.
While a lot of people already gave you pretty good advices, but ill try to say what works for us.
From the start infact use their cds on horidon until he gets to first door, but only because we can kill first door without any cds. If you cant, save up your cd for first door. Like people said, only use shorter cds as youll need them more for door two and door four. So when on door one. Kill the first wastewalker asap. he needs to be dead before the other two spawn. Youll need to decide how many people will need to use cds for that to happen thou. From then on you will only have two more wastewalkers and endless supplies of basilisks and that melee mob. id suggest focus to kill basilisks, then kill wastewalkers and then finish up melee mobs. The only thing you need to kill basilisks for is due to their stuns and low hp, so that shouldn't be a problem. You can assign one or two people (maybe more if you need to) to deal with those basilisks. Ofc interrupt their casts. When dinomancer jumps down, interrupt, get him to drop orb, finish up everything (don't focus on horidon, but rather on finishing up adds). If some dps still have unused low cd cds, use them now. This doesn't mean to leave horidon alone entirely, if you have any dot classes, they can have some dots on horidon, but hes is by no means a priority here, only when there are no adds up.
For second door (when you get to them) the prio is to assign two interrupters for second set of venomancers. They will only focus on killing and interrupting their assigned mob. Assign one or two ranged for killing effusions (they can interrupts those too if they can). The melee adds will need to die to cleaves or youll need to finish them up after horidon rams the door.
For tanking thigs, on door one your tank will need to tank everything sadly, for second doors your tank will need to only tank meelee mobs. There is no need to tank venomancers or dinomancers (for him any plate dps can tank or feral, else have a tank tank him). For horidon tank, he should have active mitigation/cd ready for each triple puncture. Im not familiar with blood dks or wars, but as a bear I don't use anything cept active mitigation for first 4 punctures, from then on I start using my minor cds coupled with active mitigation.
As for tips as a feral, once again, this is what works for me and there are probably better thngs to do. Just mangle. We are pretty much the worst mellee for this fight since we have positional requirements. Nontheless, mangle isn't something that should be frowned upon, it helps to generate combopoints faster. So for me its usually try to apply rip while mob is still high on hp, if you see hes getting low and you wont be able to build combo points and it wont tick for its entire duration, just use fb (ofc keep sr and rake up). Also you might be better on basilisk killing dutty too, since you can interrupt them, so even if you aren't toping dps meters, you are at least usefull, unlike others that from logs didn't bother to interrupt much. On second door you can take a venompriest and later dinomancer too. Don't be afraid to pop into bearform if you need when he turns to dino, although our cat is just fine tanking him as cat.
Good luck with those doors.