Onyxia's Lair Strat

So, here's a strat from wowhead.com, on how to make this fight easy

Phase 1: The Old Stuff

Phase 1 is absolutely identical to the original fight. It lasts from 100% health to 65%, and consists of Onyxia utilizing basic dragon abilities - Flame Breath (heavy hit in frontal cone), Cleave (hitting up to 10 targets), Tail Sweep (with a large knockback), and Wing Buffet (frontal cone knockback). Basic skills will get you through this phase easily - tank Onyxia with your back towards a wall, to avoid knockback from Wing Buffet. DPS and Healers should be position at Onyxia's sides to avoid both Tail Sweep and the frontal baddies. The tank might need some heavy heals, as the spells hit rather hard, and some cannot be resisted/mitigated. Other than that, you should be fine here.

Phase 2: The New Stuff

This is probably the hardest part of the fight. There are two (categories of) things to watch out for - adds and Onyxia's new spells. Note to melee DPS - you can attack Onyxia even while she is airborne, as long as you stand underneath her.

There are two kinds of adds spawning during this phase - Onyxian Whelps and Onyxian Lair Guards. The whelps will spawn in packs of 40 (20 on each side ). The first pack will spawn seconds after Onyxia lifts off in the air, and a pack will hatch every ~90 seconds after that while in this phase. While it is good to have a tank on them, try to AoE them down as soon as possible, as you want to mitigate overall damage and keep your mobility - you'll need both. The Lair Guards are new NPCs added in the 3.2.2 version of Onyxia - they resemble the old Onyxian Warder, but are significantly more dangerous. The guards will spawn more frequently than the whelps (approximately every 30 seconds), and will spawn in pairs (possible a pair from each side?). They don't have too much health, but have really high melee damage output through abilities like Cleave, Fire Nova, Flame Lash (which reduces fire resistance), and Ignite Weapon (17.5k/25k extra fire damage to targets in melee range). It is good to have a tank on them, but it is better to kill them from afar. Keep your melee DPS away from them at all times.

The other thing to watch out for are Onyxia's spells. Her Fireballs are something you should just heal through - although it is advised that you spread out, as the missiles do damage in a 10 yards wide area. /range on DBM is your friend again. And, of course, there is the Deep Breath...

Deep Breath is now on 100% random cast intervals - which means that DBM, or BigWigs, or whatever boss mods addon you use won't be able to warn you in advance. You will however see a raid warning/emote "Onyxia takes a deep breath". As soon as you see that, you need to forget about anything else you are doing, locate Onyxia, figure out which way she is facing, and get behind her quickly. Deep Breath is very unforgiving.

Phase 3: No need to STOP DOTZ

Phase 3 starts when Onyxia's health reaches 40%. At this point she will land permanently and cast a raid-wide fear, accompanied by lava eruptions. Raid wide damage, with extras for the tank - nothing you haven't seen before. Unlike the original version of the fight, Onyxia will no longer wipe aggro between phases, which means that your tank from Phase 1 should be the first person she goes to in Phase 3.

Throughout this phase Onyxia will continue to use all of her abilities from phase 1 (Flame Breath, Cleave, Tail Sweep, Wing Buffet), alongside with Bellowing Roar (3-second fear) and Eruption (AoE during the fear). Whelps will continue to spawn as well, but they won't be nearly as many as in Phase 2, so a few of your ranged DPS should be able to handle them quickly.

Note: If a player gets close to the eggs, at any point of the fight, the nearest whelps will hatch.

Taunt works