For PvE, almost anything is going to work.

For PvP, it depends on where you're going to be playing.
In normal battlegrounds, like PvE, almost anything will work.
In arena or rated battlegrounds, you're going to do better with fewer classes to manage.

The biggest question is, what do enjoy boxing/playing?

If you have casters/hunters on the team, your mechanic to deal with is using follow for facing.
You'll want to break follow, for those characters.
Possibly have a key, for the ranged to follow a specific ranged character so you can move them as a group without impacting your melee/tank positioning.

If you have melee on the team, you have to deal with the IWT/CTM and possible run-away toons as the boxing mechanic.

Ranged worry about resistances and spell reflect type mechanics, on a given encounter.
Melee worry about point-blank effects, auras surrounding a boss, and cleave type effects (getting behind the mob can help).

Including either element in your team, is essentially one mechanic needed to play.
And a different mechanic to be aware of while playing.
With both elements on your team, it is two mechanics to use; not necessarily harder, just more to be aware of.

The configuration of your system, making it work for each type of encounter... that can be as fun as actually playing the game.