As a DPS I get 3-5k renown in a scenario.
As a healer, you get 4-6k renown in a scenario.
Scenarios are 15min or LESS and you can do them all the time. (oh, not to mention you get a free gold and a half each scenario!)
Wait... Wha? I'm no loot whore... I mean, I really really really really wanted my HoX sword, but seriously... I'm no loot whore. Well, actually, yeah I am.