Initial stab in the dark - hopefully folks can help refine things.
*CLERIC*
A / Blazing Beacon
B+ / Command
C+ / Daunting Light
B- / Split the Sky
Daunting Light does solid damage, radiant, over adequate range. The combat advantage is useful, but not really powerful. Split the Sky looks really nice, until you realize the enemy is just going to stand and charge. I've seen it use a couple times and that's happened every time. Command lets you daze and choose between prone or slid a fair ways, which is a very powerful controlling combo. No damage, though. Blazing Beacon provides a sizable +4 bonus to all ranged attacks against a target for a turn, which can be used for many attacks in a round by most members of the party, including action points, dailies, etc, so gets to be top of the pile.
Just thought I'd comment on the Cleric powers as well.
1) Blazing Beacon A (or C+ depending on the group)
Blazing Beacon seems one of those powers which really depends on your group composition. If you're ever in a party with 2+ ranged attackers then it shines but this does not seem to be a common occurrence at least from the games I've seen. If you only have a wizard, it seems a waste compared to some of the other options.
2) Command A
It's really really good and would be A+ if it did any damage. Nothing much to say here. Dazed + prone means they're out of the fight for a round and the ability to slide is quite useful.
3) Daunting Light B-
It does decent damage at least and the combat advantage is sometimes helpful. A solid power though not as nifty as Command.
4) Split the Sky B-
This is only slightly better than Righteous Brand but there are some tricks you can pull off with it. If the target is dazed then Split the Sky will take them out of combat for sometime which means it combos nicely with Wrathful Thunder. If hit and then move towards them 1 square, they'll be unable to charge after standing up. My experience with a melee cleric is limited so I'm not sure how often useful situtation like this occur so the B- is tentative.