Melee classes always seem very popular. Multi-player skill combos, like skill chains or battle regimens, are a way to let groups of melee buff each other. We'll have to see what self combos and battle regimens 2.0 look like when they get implemented.

Maybe a dedicated buffer class could work in a battle regimen system by using skills that do little or no damage themselves but are able to stand in for combos from any another class. Like the dancer ability from ffxi.