World of Warcraft 10 Man Raiding Group

What a 10 Man Raiding Group Looks Like
A 10 man raiding group is going to fundamentally look a bit differently from any other group out there. While the 10 man raids are technically considered to be easier than the 25 man raids (and currently are pretty easy when you get it down), they do require quite a bit of flexibility from every member on your team. You'll be going up against 1 million HP bosses with two teams of players and if a healer goes down you may have one extra on your staff. The same is true for your tank, so it is important that every single person on your team can play at least two roles. This is much easier these days with stats compounding for casters and tanks.
For tanks, you should have two tanks for every 10 man group and at least one off-tank who will act as DPS but can step in for tanking if necessary. Feral Druids, Blood Death Knights and Retribution Paladins are all good for this.
For healers, you'll need two for most groups - this provides one for each tank but can make it hard to maintain the healing you'll need to keep your group members alive against AoE bosses or ones with diseases or DoTs. Three healers is better, though you then need to consider whether you have enough DPS coming from the remaining 5 DPS members, especially against bosses with enrage timers that are shorter than most.
The best way to balance this out is to have two dedicated healers and an off healer who can throw out heals as needed for DPS members when they get hit - Shamans, Druids and Paladins can all play this role if they are properly specced. Shadow Priests are also good here because the Priest gear is all pretty close to the same now since Spell Power covers healing and damage.
Keep in mind that when you go into a 10 man raid, you need to flexible and versatile. Keep your eyes open, build up a group of highly talented, multi-functional people and bring the player not the class and you'll do well.