Dragalge is not making it to UU sorry. Between massive physical attackers like Mienshao, Rhyperion, Flygon, and Weavile who each hit it on a physical side this guy dont make it (not to mention each of these guys are pretty abundant).
Mienshao isn't getting past Dragalge any time soon unless it runs SD + Stone Edge or something and even then it can't take a hit to save its life. The others check it I guess, although Rhyperior could get hit with a Water attack easily.
I could admit to going so far as to say this guy could be BL2 because in RU he'd easy wall things.
For the main point of this post: you're judging a sixth generation Pokemon in a fifth generation tier. For all we know, Dragalge and all four of these Pokemon could never share a tier together.
Still these are the factors which to me hurt Dragalge's upper tier status:
-abilities are the same in different fashion and can both be accomplished through SludgeBomb or Toxic
Keldeo has Justified. Your argument is invalid. Poison Touch is cool for getting rid of a Latios on the switch with Dragon Tail and possibly poisoning it in the process though.
-the only current offensive set you can run is either Specs or sub/3attacks
You don't need to run offense with everything.
-it is 2x weak to Ice, Ground, Psychic, and Dragon each of which is in the UU tier
You're still judging a new Pokemon by old standards, but anyway, Dragalge also comes with a sweet seven resistances (Grass, Fire, Water, Electric, Fighting, Bug, and Poison), and Dragalge has more than enough bulk to shrug off weaker Special hits and can even tank a few huge ones - with a specially defensive spread, this thing can survive an Ice Beam from Modest Kyurem.
-in comparison to Goodra (stats) it only beats it in defense and 70 vs 90 is not exactly a big difference when you only have base 65 hp
If you want to compare it to Goodra then you have to recognize that:
-they can each learn the same Special attacks that could possibly be used between the two of them
-Goodra has a niche spot in Drizzle or manual rain because of Hydration
-Goodra has 1 less weakness/Dragalge is weak to Earthquake probably one of the most used attacks
-Goodra cannot be walled by Steel-types like Dragalge (Goodra gets Flamethrower and EQ [anyone 1-up to Dragalge])
Goodra and Dragalge are similar, sure, but they aren't similar enough to just blindly compare them in this way. Dragalge has a much better typing (immune to Poison regardless of Ability and 4:7 weakness to resistance ratio as opposed to Goodra's 3:4). Dragalge has a better support movepool just coming from Scald and Toxic Spikes alone.
I truly don't mean to assault this pokemon at all because I was very excited for it but it proved to be a slight disappointment. As I said before this guy has great promise as a wall in RU but up in UU it would just get countered by things like Empoleon, Bronzong, and Scrafty or die to a Krookodile, SubBisharp, or FLygon
Still trying to arbitrarily place Dragalge in BW UU, huh? That's not even considering that Dragalge would have been one of the best Keldeo checks we could ever have gotten in BW OU, let alone the fact that it also checks Gengar, defensive Celebi, Venusaur, and every single Fire/Water type in BW OU.