I settled on Striker, Defender, and Support Leader, partly because I could abbreviate them SDL and know which one was what, and partly because I came up with a bunch of combat attributes that balanced quite nicely when divided among three roles. Suggested by Guild Wars 2, every role should be capable of supporting itself (self-healing or whatever), a Leader just helps them do it better.

It would be like every character having access to Second Wind (a la Fourth Edition rules) to heal themselves once per combat, plus being able to administer First Aid to a downed ally within reach (the Fourth Edition Heal should allow this as a minor action, maybe like how characters help each other up in Left 4 Dead).

I understand Second Wind being a Standard action, it’s supposed to be a kind of tactical suicide. Considering how First Aid requires a minimum of two characters, though, I don’t think one player should be penalized for helping another by requiring the expenditure of his Standard action. It punishes players who want to help each other. Making it a touch-range effect is restriction enough.

In your Fourth Edition game, consider allowing your players to administer First Aid to an adjacent ally as a Minor action instead of a Standard action. You know what still makes sense, though? Requiring a Standard action to make a complex Heal check during a skill challenge. If I recall, however, Sly Flourish encourages making skill challenges require minor actions during combat, I could go either way there.

I’m meandering around my topic. Strikers determine priority targets and eliminate enemy threats. Defenders slow the enemy advance and protect allies. Leaders provide tactical advantages and opportunities to allies.

The design of every striker should start with a “target acquisition” power of some sort, even if it’s eventually replaced with something else. Every defender’s design should start with some kind of area control “checking” effect (to use the sports terminology), be it a trap, or a shout of challenge. Every leader’s design should incorporate some way of enabling opportunity attacks for allies.