Daily 15 Powers
Okay, took a bit to do the spreadsheet to calc some expected damages over a range of targets so I could maybe compare some of these. I'm kinda assuming a midline of character optimization... damage dice are going to matter a lot than multiple attacks more to a character who is only +8 damage modifier at level 18, but more attacks kick butt for someone with +30, so different characters have some different needs in that respect.
*CLERIC*
B- / Holy Spark
B+ / Purifying Fire
B+ / Seal of Warding
Holy Spark Weapon attack vs. Will makes it very accurate - if you hit it's pretty decent, especially if you time it right to hit several enemies before your target even acts. On miss it's pretty lousy, and its damage effect is tempered a bit by enemies being able to avoid it after the first time.
Purifying Fire is a nice sized area of enemies only for considerable damage. The healing from it is pretty fiddly, but this is a dependable and solid performer.
Seal of Warding is a good sized close burst, enemies only, vs Will, for impressive damage. The zone's difficult terrain might be problematic or helpful and that's a little harder to control since you have to be stuck in the middle of it, but ranged cover and difficult terrain on demand might make the zone valuable. Even if not, it's a great damage close attack.
*FIGHTER*
B- / Dragon's Fangs
B / Serpent Dance Strike
A+ / Unyielding Avalanche
Dragon's Fangs is boring, but solid damage.
Serpent Dance Strike is a little tricky to use well, but it's good for some shifts, attacks on a couple of enemies, and knocking prone is pretty helpful - especially for a fighter who can mark targets then be in a spot they can't attack/charge to easily.
Unyielding Avalanche is a little crazy really - standard 1W stance, but also with slow, which is fantastic for a defender... but with +1 AC and saves? Great! And... Con regeneration? Hard to say no.
*PALADIN*
C- / Bloodied Retribution
C / Break the Wall
B / True Nemesis
Bloodied Retribution is mostly a self-healing surge (with no bonus to it, and not even a free surge). 4W vs. AC isn't horrible, but it's definitely substandard damage compared to other level 15 dailies.
Break the Wall vs. Fort and short range with lackluster damage. The penalty to defenses is definitely good stuff, but it's a low penalty and save ends so unlikely to last long on enemies you need it for the most. I guess considering it +10% to your allies' damage for one round is not a bad way of thinking about it.
True Nemesis is vs Will, which is good... it is low damage and short range, but it puts a sorta 'Super Mark' on the target. This power will see its best effect when combined with a second defender who can actually mark the target, making the target screwed if they can't hit both.
*RANGER*
A- / Blade Cascade
A- / Bleeding Wounds
A / Confounding Arrows
A / Stunning Steel
Blade Cascade is actually outright rotten damage under most circumstances, but gamed properly (don't bother unless you hit on a 2 or 3, preferably with a reroll available, pretty much) its burst potential is extremely high and it's a power multiplier due to the number of attacks. A pet TacLord and a source of a reroll will definitely help here to optimize its damage and up its personal grading. I know this one will be surprising to some... it actually averages less than the Fighter's Dragon's Fangs under most circumstances, though, and that has to count for something.
Bleeding Wounds is deceptive - it's actually a bucket of potential damage once you do the math and very flexible about where you place it. Its expected damage and versatility is higher than Blade Cascade under normal circumstances, but it doesn't peak nearly as close.
Confounding Arrows is okay damage in a versatile package, though it's slightly tricky to use. Its main strengths are in Dazing even on a miss on up to three targets, and in extremely high chance to stun (save ends) a single target.
Stunning Steel is a weapon attack vs Fort that stun (save ends) on each of two attacks, allowing two targets to be stunned or one to be almost certainly stunned. Its damage isn't amazing, but it's certainly respectable enough given the very powerful effect.
*ROGUE*
C / Bloody Path
B+ / Garotte Grip
C / Slaying Strike
Bloody Path is certainly fun and it is a way to move speed without provoking any OAs, which is okay... but it's immensely dependent on enemy positioning and damage output. Thankfully monster basic attacks are often very good damage and sometimes have special effects, but their chances to hit themselves are often unimpressive.
Garotte Grip is autohit and minor if you can setup grab in some manner, so it may often be worth doing that instead of just using it as a standard attack. Its damage is not that special, but gaining cover and body shield is quite cool. Unfortunately, the chance of sustaining it three times for the coup de grace is extremely unlikely to be of great use.
Slaying Strike is deceptive. It looks like it must do a lot of damage and hey that's a big crit range, and certainly it's easy to find a bloodied enemy... but Ws aren't that great for rogues in general, a single attack is just worse than multiples, and a rogue crit on a bloodied target has significant chance of blow-through. Tack on that a character will likely have an expanded crit range for much of the time they possess the power and it's very disappointing output compared to other daily 15s.
*WARLOCK*
NA / Curse of the Golden Mist
C- / Fireswarm
A / Tendrils of Thuban
C- / Thirsting Maw
Curse of the Golden Mist is pretty awful in one sense - it's only really worth using on a creature that is flat out more useful than the caster, and ensures that the game is now going to be more boring for the caster and target... but it technically can have semi-broken results when used against solo creatures. For instance, the poor Tarrasque is completely screwed by a repeating Will attack to render it useless. I'm currently grading it Not Applicable with the suggestion that no one take it or base any power balance off it because powers shouldn't just be a more powerful version of it, either. They just should be designed completely differently.
Fireswarm can be high damage potential if you can position enemies well for it and/or get a nice string of hits, but it's slow and steady damage and replacing actions (sustain standard) you could otherwise eldritch blast (or whatever). At least fire and poison both will dodge a lot of resistances.
Tendrils of Thuban is an area immobilze that does good damage, and the sustain minor attacks again and immobilizes. With a little work you can keep a melee enemy locked down for a very long time with no way to get out (which is why I'm rating this as highly as I am, much to some folks' surprise I suspect). Solid damage, powerful control effect, nice sustain.
Thirsting Maw is a pretty cool concept, but it's short range, vs Fort, the target is likely to save pretty quickly, not much going on if it misses, and the amount you heal is quite low.
*WARLORD*
D+ / Make Them Bleed
B- / Renew the Troops
D- / Warlord's Gambit
Make Them Bleed is basically a very lackluster attack and 'ongoing 5 damage (until the enemy dies)'... and the ongoing damage is very cool in that way, but damage up front is just flat out better and since it doesn't stack in any way it's actually not even all that much damage over the course of the entire fight (barring a crazy 20 round fight, in which case it will catch up to the damage that some daily 15s do in one action.
Renew the Troops is basically Mass Cure Light Wounds (Utility 10) with slightly better range and healing a bunch less if you fail to hit. In truth, it would possibly be a better power if it did no damage and didn't make an attack at all. In the meantime, it is a big chunk of free healing which is still appreciated in the right circumstances. If you're not worried about surges, though, Stand the Fallen (level 5) is probably a better power so its rating can only be so good.
Warlord's Gambit is generally rubbish, since it's a lousy attack tied to giving the enemy a bonus if it attacks you. The bonus has a significant penalty, but the enemy gets to decide when to trigger it pretty often. That said, this power could see good use with multiclassing for a defender who wants to be attacked anyways. I'd like to see that an inspiring warlord with paladin multiclass could get good use out of it, but his Int would probably suck for how close the allies would have to be to get the free basic attack.
*WIZARD*
B+ / Bigby's Grasping Hands
C+ / Blast of Cold
B- / Otiluke's Resilient Sphere
A- / Prismatic Beams
A+ / Wall of Ice
Bigby's Grasping Hands is likely an action hog, potentially using up all of them in any particular turn, but grabbed is helpful, its damage is solid, and honestly clapping enemies together is a little hilarious.
Blast of Cold is moderate AoE damage with an immobilize which can be good... but slow on a close attack is pretty dubious and it's just save ends so it doesn't have the persistence of many dailies at this level. It is enemies only, though, so this has nice synergy with putting it right on top of your defender.
Otiluke's Resilient Sphere is a peculiar spell that won't be for most people, but it removes most enemies from the fight for multiple rounds (effectively for the fight, in a lot of cases), immobilizes on a miss, and can be used defensively in rare circumstances.
Prismatic Beams is a large close burst of enemies only that actually does solid damage and dazes. It's pretty unforgiving of low rolls, but its expected damage output can be quite high and dazed enemies are easy to disengage from.
Wall of Ice is absolutely brutal. You get automatic damage against any enemy you put next to it, can truly screw certain enemies if they're trapped inside it, etc.