http://us.battle.net/wow/en/characte...o%C3%B1/simple
http://www.wowprogress.com/guild/us/...ting.tier15_25
Haste is amazing for destro this tier, crit is easily the worst of the 3 in terms of practical use.
He should be going
haste > mastery trying to keep them fairly close to each other for general purpose destro this tier. Technically pure single target you'd want to have a massive haste bias and aoe you'd want to have a massive mastery bias.
@OP: It looks like he's under using rain of fire like most novice destro locks. You're supposed to use rain of fire single target and I put a lot of stress on when people don't do that because its easily the biggest ember generator a destro lock has for a single gcd outside of shadowburning a target before it dies.
As an example on a random horridon parse I have around 1500 ticks of rain of fire, he has 112, even when you're single targeting the important mobs rain of fire should be up as close to 100% as possible for insane ember generation.
He's got 4 havocs cast for the entire raid, I had 13 on horridon alone probably not even using it as often as I should. That's really just shooting yourself in the foot with the amount of useful dmg you can put out for a .5s gcd by throwing out that extra chaos bolt or being able to triple shadowburn 2 targets at the same time or even just for the extra ember generation on a fight like megaera.
He's basically making the mistake most people make and over prioritizing incinerate and everything else over keeping rain of fire up, which means he's neutering his ember generation which forces him to incinerate more when he should be spamming chaosbolts like crazy. Couple that with under utilizing havoc and gearing for crit instead of haste / mastery you're looking at some fairly lackluster damage.