I do the 2 dk and 1 shaman on a 3 man mount sometimes.

It works in some battlegrounds and not others. Basically no /follow is a minor inconvenience at that point. You'll have to switch to the guy out of range from time to time or just mount up and fetch him. Before 5.4 my tyrannical geared 3s team was topping DPS and heals in BGs like temple and AB.

The usual suspects (towers in AV, bridge in EOTS, any area of strand) are all no-go zones because IWT isn't smart. But you are probably used to that.

I like to fool around in PvE with the group too. Sadly, scenarios can be really annoying.