On one of the blogs I read someone posed the question "What would your ideal WoW party consist of?" Here’s my answer as of late in Burning Crusade World of Warcraft. I am assuming you are forming up a group of level 1 people who are going to be instancing together from now to the expansion (and you are all reclusive millionaires so you can play as much as you want to before Wrath comes out and completely invalidates this).
Tank: Either a protection warrior or a protection paladin. The warrior for their numerous "oh crap" buttons and sheer survivability and the paladin for their amazing AOE tanking abilities. A bear druid would be a strong second place – the main reason I wouldn’t put them in first is that all those lovely plate and shield drops would get sharded.
Healer: I would go with a holy priest. From what I’ve seen there are no situations where a priest is a bad choice for healing 5 mans. In cases where the group is taking a lot of AOE damage, a paladin healer may not be able to keep up. A restoration druid or shaman would also be a strong choice, but they’re not as versatile as a priest. A discipline priest would probably work as a main healer as well, but I don’t know enough about them to say for certain.
DPS/off-heal: I would pick either a elemental shaman, a balance druid, or a shadow priest. All three should have a good sized mana pool and their gear should allow them to do a decent job of picking up heals if needed. I would lean slightly toward the shaman for utility and so that mail caster gear doesn’t get sharded. The shaman’s hourly self-resurrection would also be useful on rough runs. Retribution paladins and enhancement shaman are less likely to have the mana pool and gear to pick up on healing.
DPS/utility: Mages take this hands down. A warlock or rogue will probably pump out similar or slightly greater DPS but they’re nowhere near as useful. Mages offer the best CC in the game for humanoids and beasts, portals to capital cities, food, and water.
DPS/support: I would lean toward a hunter for this role, particularly a hunter with improved traps. A hunter’s traps provide CC for almost every mob in the game. Hunters can pump out some very strong DPS. A hunter with jumper cables can help with wipe protection. That being said, it’s easy to argue for just picking another one from the DPS/off heal category. An elemental shaman can bring totems for strong group buffs. A shadow priest provides a steady stream of mana and health while DPSing. A balance druid brings Gift of the Wild and a battle rez.
Here’s the party I’d make for running 5 person instances: protection paladin, holy priest, mage, elemental shaman, and shadow priest. The shadow priest could be replaced by a balance druid giving stronger off-tanking possibilities traded for weaker off heals/mana regeneration.
Classes/Specs I would not bring: Fury warriors,arms warriors, retribution paladins, rogues, warlocks, and enhancement shaman all bring DPS and utility to the group but their contributions pale when compared to those of the classes I’ve listed. These classes all have strong places in raids or in PvP but they just aren’t useful enough for 5 player instances.