Garthanos
Arcadian Knight
The ultimate effect of all 4 role contributions is victory by hp attrition.
I think the key difference between leader & striker is not their net contributions to that race to 0 his, but that the leader's contributions require a party and are synergistic, while the striker makes a more individual, additive, contribution.
It's similar with defender & controller, absent a party, a lone defender's 'control' is meaningless, but a controller still controls, if anything better, on his own...
I both like party synergy and find it mildly annoying that for Warlords and Fighters to be properly interesting they simply must have ally synch