My guild was never one much for world bosses, but one day we got a wild bug up our collective bottoms and decided to tackle Kazzak, just to see if we could do it. We gathered up every raider we could find and managed to scrape up about 30 - about half of us outfitted in Kara gear or equivalent, and the other half sporting ZA gear with the odd piece of T5. Main tank was our best-geared protection warrior, and heals consisted of myself and one other holy paladin, two resto shamans, a resto druid and three holy priests, one of whom was LV69 (!) and had to be summoned up onto the ledge with Kazzak by one of our locks. DPS was heavily ranged with the odd smattering of melee. We even had two of our guildies dual-box their Alliance accounts and bring an extra boomkin and hunter to get in on the fun.

The trick to Kazzak, once you've cleared the adds around his dais, is to push as hard as you can as fast as you can. If the fight lasts over about a minute and a half, you will need some serious luck to finish. From the start everyone rushed in and stayed packed tightly together in their respective melee/caster group, to maximize AOE heal efficiency. Both paladins focused on chain-casting max-rank Holy Light on the main tank as their only task. DPS unloaded as soon as the tank had enough aggro (boosted by Misdirects on the tank and Blessing of Salvation on DPS) but kept their cooldowns for the shadow volley. When the shadow volley came, everyone popped every CD they had, bubbles, trinkets, pots, freakin' Cloak of Shadows, whatever was clickable and ready. This combined with AOE heals from the shamans and priests allowed us to DPS straight through the shadow volleys and make up a lot of time that we would have otherwise lost "getting the hell out of there" as other strategies advised. We did not have a single death with this approach.

Drops were the healer staff (which, amusingly, went to the 69 holy priest), the plate tanking gloves, and one random green. XD