A few questions from a newbie

[Maxion]

Since someone mentioned that someone's all-shaman group did ramparts at-level, my 5-shaman group cleared gundrak at lvl 75, and heroic UK shortly after hitting 80.

All of the same class of a caster class (maybe even melee class like paladin) is a good way to get into boxing.
Any group with a tanky class in the group will have a lot easier time in instances, but it is not completely required to do alright.

Mixed class groups take some more work / setup / practice, and I would recommend trying a simpler setup first for someone new to boxing/macros.

[Shodokan]

Since someone mentioned that someone's all-shaman group did ramparts at-level, my 5-shaman group cleared gundrak at lvl 75, and heroic UK shortly after hitting 80.

All of the same class of a caster class (maybe even melee class like paladin) is a good way to get into boxing.
Any group with a tanky class in the group will have a lot easier time in instances, but it is not completely required to do alright.

Mixed class groups take some more work / setup / practice, and I would recommend trying a simpler setup first for someone new to boxing/macros.

I agree.

I find playing both my 4 ret + dk, 3 mages and 4 shaman+ prot pally all very fun. Mostly due to the simplistic nature to these group compositions and their synergy as someone else mentioned. Though the 3 mages will out-dps the shaman by quite a bit at equal gear levels especially in heroics...both AOE and single target.

In my opinion if it is your first time, you really should go with something that has passive healing like shaman or paladins (ret).