Cleric:
I know you really value attack bonuses, but in this case, I think Command is better than Blazing Beacon.
I really hate having to upgrade the +attack/-defense ones so much because of their effect on other powers, but it's a "potential" awesome - you can use it to upgrade your Thirsting Maw, Fireswarm, Confounding Swarm, etc. Just looking at Confounding Swarm alone, +4 to just that one character's attacks (and he could spend an action point) makes stunning far more likely and is a solid damage upgrade. Damage + Stun that is better than any other Encounter 3 power, without factoring in action points or other characters, or things like warlord's giving extra attacks.
I would value Sweeping Blow a bit higher than Rain of Blows, because like you mentioned it can mark a whole bunch of targets. Also its abilities are attached to a better weapon, not to mention it gives you a nice attack bonus. Dance of Steel is pants. May as well give it an F.
I personally like Sweeping Blow better, but Rain of Blows is the highest damage output option available and what's wrong with flails?
Arcing Smite does a good job of letting the Paladin play his Defender role, so I think it deserves a better grade.
Fair.
If Split the Sky is a C+ with the knockdown, I don't see why Staggering Smite is a B- without the knockdown. The extra damage on it is nice, but knockdown is much nicer, not to mention the former ability is vs Fortitude, whereas the latter is vs AC.
Hmm, that sounds like I made a mistake. Let me bring that up... Okay, Staggering is a Str-based, so its Wis squares could easily be 4 or 5 squares. It does +1W but AC instead of Fort. Though I'll note that Fort is not a whole lot better than AC, so maybe that's what I was thinking. Hmm, I think I should probably up Split the Sky a step - cause my original score was better for it.
Rogue:
In the absence of an action point (which is half the encounters) I like Setup Strike better than Topple Over, since the combat advantage it grants me lasts longer. I might rank Topple Over a bit higher since it helps allies too, but not a whole grade higher.
Honestly, I don't like either... but most of Topple's upgrade is from the +4 or so to hit from Brutal Scoundrel. Especially for a rogue, actually hitting nets you another 2 to 3d8 damage. That said, I think I overvalued Topple and I'll adjust it lower. Would you argue I undervalued Setup as well?
Trickster's Blade is also more interesting than you give it credit for, because you can make a ranged attack with it, and the AC bonus is against everyone. I think it's a very reasonable opening move with that crossbow when you have combat advantage for 4d6+dex damage (4d8+dex with 2 feats). That's better than a C- in my book.
Hmmhmm. Toss a dagger in, gain the bonus, maneuver somewhere less safe... okay, I was underestimating that.
Fiery Bolt deals oodles of damage (which fits the Warlock's job description), so I have a difficult time putting it lower than Otherwind Stride. I'd rate them about equal.
I had rated them pretty close, but changed my mind after seeing both in use a bit more. Otherwind Stride immobilizes a creature then teleports you _far_ away, and you can even take a move afterwards. That's a great synergy of effects... but the main reason stride is rated so highly, it's just a big teleport. It's pretty comparable to the level 6 Wizard daily utility, Dimension Door. Except it's every 5 minutes.
Warlord:
I only have one big disagreement here. Inspiring War Cry should be the top of the list. This attack ability as an encounter power is a rare gem. And since it's an Effect, it triggers independent of the result of your attack roll. Getting your Striker or Defender un-dazed before they act can be very important. Between Shake It Off and Inspiring War Cry, you can provide a healthy bit of relief to your party.
I like saves as much as the next guy, but I was having trouble comparing to other powers - like Shake it Off, but even like Sacred Flame, an at-will. You only need to give people saves so often at the level range this will come up and it's not a save with any kind of bonus. Mostly I just figured that a level 3 attack power that gave a save should do slightly more, like go against another defense, give a Cha bonus to it if you're an inspiring warlord, give an option for temp instead of a save, etc. I'm willing to upgrade it if others agree, though. It's certainly solid.
Wizard:
If Otherwind Stride is a B-, why is Icy Rays C-? Immobilized is a fantastic condition to inflict on an enemy. And you get to inflict it upon two enemies. It's something you can use almost every encounter since it's ranged. I find Close Blasts like Color Spray are much harder to use.
A-, B-... and it's all about that teleport. Immobilized is decent, but it doesn't necessarily bother a ranged opponent (unless it allows melee to get up to them) or a melee opponent (unless his attacks can't reach) so I'd certainly rate it lower than daze. While close spells are tougher to use, they also don't provoke, so that counterbalances to a certain extent. You can, for instance, Color Spray then move away without being OA-ed. I wouldn't want only close spells, but having a selection is good. I do like Icy Rays a lot - that's why I set it to B-. How powerful is the custom targetting? Would it make sense to upgrade both Icy Rays and Eldritch Rain?