I'll cover all of Bastion of Twilight first, then Throne of Winds and the lastly we'll go over Blackwing Descent. I'll cover the fights in general but also talk specifically about tanking from a paladin perspective and give any hints I can about how we assign DPS and healing.
2 tank, 3 healers
This is a remarkably easy encounter once you can manage to figure out which drake to kill first. Basically, you're going to have to decide whether your raid can manage more tank damage or more raid damage. Generally speaking, you want to mitigate tank damage first and as quickly as you can, and then go for raid damage. There are many drakes and you can read the details here. Long story short:
- Slate and Nether increase damage done to the tank.
- Storm, Time and the Whelps do damage to the raid.
There are a lot of strategies about how many drakes to release at once and so forth, but starting out fresh, I'd do one drake at a time and release no more than 2. I would only release 3 if your raid is running into enrage timer issues.
My rule of thumb is this: anytime Nether is up, you want to release him first. The increased speed buff makes Halfus hit tanks incredibly fast and if you also have Slate up this can destroy your tanks with the healing reduction debuff within seconds. Release Nether first and burn him down - the 25% miss chance will make tank damage go from crazy to "leave some HoTs on him." With Slate you will have to swap tanks eventually. Ideally after the first drake dies if your DPS is on the ball.
If you have Storm up with Nether, you might say that Storm takes priority with his Novas, but as long as your healers watch the Nova cool-down and don't try to channel Tranquility just before his casts or something, your raid should be able to survive the Novas while you're burning down Nether and then you can release Storm second and let the tanks take interrupts on Halfus.
Time and Whelps are both really easy - Whelp breath damage isn't too terrible and can be healed through easily but Time damage can get significant so you probably want to release Time second and your raid can start side-stepping fireballs.
It's basically a priority order of kills:
Nether > Storm > Time > Whelps > Slate
Whenever possible group up the drake with Halfus to let cleave damage go through and keep the tanks with their backs to a wall when Storm is up or you might find yourself being flung into lava. I don't know if this is still happening or if they threw up a wall but we had some (hilarious) tank deaths to this early on.
At 50% he goes into phase 2 and if you want your tanks can swap either to rotate through their cooldowns or to drop Slate's debuff, and he should die shortly with the 100% increased damage taken from two dead drakes.
He'll occasionally do 3 roars that stun and if Storm is up, he'll cast a nova right afterward - you can have mages Blink > Counter spell or you can just spam Rebuke and hope it goes through. Either way, if everyone is topped off it shouldn't be an issue.
Make sure you give your healers a heads up to top folks off before roars go out and you should be golden. This is an incredibly easy fight. Good luck!