Loot Drops
There is many guilds who consider taking less Warlocks in place of more Rogues in order to increase the raids DPS. Personally, I find that taking your 18 absolute best DPSers is a much better idea while still maintaining a balance of Rogues, Mages, and Hunters.
Everyone in the raid should have Triad active as well; even though it provides less help then it does for the other dungeons due to its Bossmods not being updated fully for Gaia gold. It still will provide a much needed benefit to your raid.
Unlike the previous two major instances, Naxxramas bosses drop between one or two Ttier 3 armor pieces along with one to two extremely powerful purple items. As a note, each piece of Tier 3 loot requires various scrap parts f Aion inside the instance along with a quest to kill trash mobs by the Argant Dawn. When all of this is collected, then the Argent Dawn will craft the pieces for you.