First of all, I would like to ask anyone who is reading this to go to http://www.ctmod.net and get the CTRaid Assist, UI MOD helper for MC. This is to provide horde priests with the ability to see debuffs on us without having to be in the same group, thus not requiring that we have 8 priests with us in an MC raid group.

Nextly, I am going to write about each class's role during MC boss fights. The first will be lucifron. (More bosses to be added later, I need more experience with the other bosses, I will not write about something i have not experienced.)

Lucifron

THE FIGHT:
Lucifron is said to be the 2nd easiest boss in the entire Molten Core; as well it should be one of the easiest encounters considering it is the first boss you will come up against. The pull of lucifron is not all that complicated (or shouldn't be, granted you have competent people playing with you). Nearly everyone should stand at the back of the cave, farthest away from Lucifron. Two warriors are then needed for the pull of lucifron and the holding of aggro (considering Lucifron mind controls one of the warriors right at the beginning, the other warrior will then need to hold aggro.) At this time, one hunter will be specified to add a hunter's mark to one of the adds so that the group will know which add to focus their firepower on. A warrior will get close enough to Lucifron to aggro it, then both warriors should take lucifron and both adds to the far right wall and keep him there the entire fight Both tanks should then use shield wall at approximately the same time, to keep the hits from doing too much damage initially. At the time of the pull, the designated hunter should then begin firing hard-hitting DPS shots into the add with the hunter's mark and pull him off the MT, the hunter should then back up as much as possible then drop aggro (feign death, disengage, anything to drop aggro) onto a waiting tank. The tank should build aggro for about 7 seconds before everyone begins to lay out their DPS. Meanwhile, the other add should be assigned to a waiting tank and pulled to the back of the cave close to the other add and away from Lucifron. Once the first add is dead, all people should then move on to the second add and kill it just like with the first one. After both adds are dead, all people move on to Lucifron (who by this time should have almost no mana) and kill it. The fight is very straight forward as long as the pull is good.

IMPORTANT THINGS TO KNOW ABOUT THIS FIGHT:
1) Lucifron has the ability to mind control multiple people at one time, as do his adds; have a shaman purge or a priest dispel the debuff immediately. 2) Lucifron has an AoE curse that makes abilites cost 50% more (this includes rogues and warriors). The debuff can stack so abilities will cost 100% more than normal. Be sure to have a Druid or Mage remove the curse asap. 3) Lucifron has an AoE magic spell that puts an ~ 10-second time bomb on each character that will do around 2000 damage. Priests need to dispel this from tanks and low health targets immediately, or they will die.

CLASS ROLES:
Healers and dispelers are extremely important to this fight; as they are to any fight. Curses and magic debuffs need to be removed asap. If you can do it, do it.
Priest: Heal of course, but dont forget to dispel those people with the magic debuff. 2k damage is a real bummer. If there is an ample amount of priests, one priest could be assigned to removing people's debuffs only so that everyone else could focus on their healing. Two priests should be assigned to heal the two tanks on lucifron during this fight. Each should watch one tank specifically, then once one of the tanks takes all aggro, healers should rotate to save mana.
Druid: Heal, and remove curses. Druids should never think about doing DPS against ANY MC Boss unless specified. Druids should also res a tank that dies while fighting the boss, be sure that the Tank that gets the res was the one assigned to hold the aggro.
Mage: DPS, and remove curses. Removing curses should be a top priority of a mage in a group with people that have the curse debuff. One mage could be designated to remove each group's curse debuffs so that other mages and druids can focus on their healing/DPS and not have to worry about curses. This is not recommended. The best option if there is a shortage of mages is to have one mage watch two groups only, and remove their curses. This way no time or mana is wasted. The rest of the time for the mage is DPS.
Rogue: DPS, and only DPS. Keep your target in sight at all times and let your DPS rip. Continually use feint so you do not take aggro. Use feint even if you do not currently have aggro.
Shaman: Purge mind controlled allys, shaman can be assigned to heal at any time. Though shaman are not the best of healers, Shaman heals can really make a difference in an MC group with fewer healers. Group leaders will designate whether a shaman is to heal or melee/caster DPS.
Hunter: Hunter roles are to stay far from the fight and lay out DPS as much as possible. Hunters should stay as far from the adds and Lucifron as to not get hit by the debuffs and to not get mind controlled. Hunters should make sure to not hit so much until the tank has the aggro because there isn't anything worse then having to chase a unit that is going after a hunter that just got a high autoshot crit.
Warlock: Warlock plays the role of DPS and DoTs in this fight. Use the highest DPS pet (IMP) and let your dps fly. Be sure to soulstone a priest or druid.
Warrior: Obviously, warriors are meant to be tanks. In this fight, there should be assigned 4 tanks (2 on lucifron, 1 on each add). Other warriors should pull out the two-handed weapon for DPS, but be ready to equip that shield in case you need to take aggro if the MT dies. Don't be afraid to step up if this occurs, because this will happen.

Tip: If a healer can stand behind the smoking rock during the Lucifron fight to heal the MT on Lucifron, that healer would then not be in Lucifron's line of sight but still be in the line of sight for the MT to heal. Not being in Lucifron's line of sight means not getting hit by the AoE debuffs.