I do one scenario a day on a dps character while I'm waiting for my Heroic daily to pop. If I'm Valour capped I don't even bother logging in on that character unless I'm raiding or someone needs some added firepower or enchants. At 40 points the first one is well worth doing (as it is the same as a second Heroic dungeon), but once those are done that's it.
I've got decent loot from them, but the boost to the loot came too late for my main, who DE'd the bracers that rained out of them.
My DK alt has benefited though.
The Operation Shieldwall dailies were excellent, as they were broken up by story (but I was done with my other reps at that point - Anglers and Cloud Serpent both optional and proper last). Every couple of sets of dailies, you'd get some story, so there wasn't the same relentless grind that was Golden Lotus/Klaxxi then replaced by AC/SP (with an overlap of all 4 when you hit GL Revered).
Scenarios are a mild distraction that you say "Hi" at the start of and then proceed to do your job without a word, fully capable of soloing, and occasionally duo-ing the content. They are more predictable than dailies, and only the first one is more profitable in terms of VP per hour invested than dailies.