I disagree with a lot of your ratings by what I feel is a fairly significant margin. Now, I'm going to point out a bunch of disagreements, but I first of all want to say that I am pleased that you are giving these reviews to start with - they give us something to talk about.
Acid-Spew Dragon is, I think, not very good. I mean, it's just so expensive - if you were paying six for Sultai Scavenger, it wasn't a good deal. I mean, 5 mana for a 3/3 flier is kind of the norm, and it's not anything super special in most sets. Now this has deathtouch, which many be super releveant in getting it to trade with other dragons... but on the other hand, it does cost 6 still, so it's not like you are getting a particularly good deal in that trade. The bigger thing is that you can morph it, which is okay, but it's so incredibly expensive to flip up... I dunno, I'd be closer to a C- on this guy. I can't imagine the flip-up ability will be so relevant.
Stormwing Dragon has all the same negatives, except I, like you, don't think first strike is as good as deathtouch. This would also be D+ to C- though.
Epic Confrontation, I actually agree pretty much with all you are saying, but that would put it into the B kinda range for me.
The Uncommon cycle, I agree again, for the most part, with what you say, but I would in general rate them all a good bit lower - C to C+, because that's how I felt about the uncommon dragons in FRF. However, I like the BR one the best by a substantial margin, as getting a Gravedigger effect is just great value. I guess I could see UB being better, but it's going to be dependant on how much you can get exploit to really do something for you.
Risen Executioner... I don't know, a lot depends on how many zombies there will be. Recasting this will be real hard, and it can't block. I would hazard this is closer to C, but could be good if Zombie tribal happens.
Sunbringer's Touch - Okay, here's the real big disagreement. You have given this a grade reflecting that ti's very very good, and will usually be close to the best, if not necessarily the actual best card in your deck. You seem to be exhibiting a lot of BCSM here to me. I actually think this card is basically unplayable. You are giving one creature, what, +2/+2? +3/+3? I mean, you have to play out a creature first, and hit your land drops... at best I could see this thing giving +5/+5, and even then you are getting blown out be any bounce spell, or even just a removal spell. And much more likely, you're giving a modest bonus to your worst dude - 2 cards to make 1 guy reasonably sized, not great even. The trample is probably not going to do all that much. I think this is like D+ territory.
And Sarkhan, people have talked about this, is not an A+. I mean, he's very strong, to be sure, but actually, not that unbeatable - if they remove the dragon, there's a decent chance he just falls right away, which is still really good value, I grant you, but not like, THAT amazing. And he's 3 color. Not so much that decks won't be able to make 3 colors, because I think two with a light splash will be fairly common, but you are forced into these particular three. If two of them aren't open... I don't think double splashing will really be a very good option. Having said that, he's strong enough I'd probably go B+ to A-, and if the fixing is better than I expect.... we'll see.