Updated the OP to reflect the new base stats according to Serebii and a bunch of moves Dragalge is confirmed to get. Thanks to dipl0matt and zferolie for figuring out that it gets Toxic Spikes, but I would ask you guys to please use the PM feature for a similar conversation in future since the page is now kind of clogged up with posts only relevant to you two. I highly doubt Dragaloge will be making waves in OU, but I suspect it may actually be a very solid UU Pokemon. Its bulk, while not anything incredible, is decent - particularly on the special side, and especially with investment. It's painfully slow, but that gives you an excuse to pump a bunch of EVs into HP, which further amplifies the bulk - offensive Roserade cannot scratch you, so it is forced to resort to sleep powder or switch out. (For reference, the strongest thing standard offensive Rose can hit you with is Sludge Bomb, a 4-5 hit KO) That special attack may not be incredible, but it is actually stronger than Kingdra, a Pokemon that no UU player in generation 5 would consider anything short of terrifying with a specs set, so there is a good bit of power behind those attacks - it's just a shame it is a bit too slow to really capitalize on that, but it can still OHKO standard Blastoise with Draco Meteor 56% of the time after Stealth Rock. Sludge Wave is a surefire 2HKO. DM is also a 2HKO on 252 HP Suicune, but unfortunately you cannot outrun it without a +spe nature so it will usually be able to rest before you get the second hit in. Still, an already-sleeping Suicune or one switching into several layers, possibly with prior damage, could very well be KOd.
Oddly enough, 97 SAtk is actually just enough to make you a fairly potent wallbreaker - 252 HP Bronzong is 2HKOd by Focus Blast over 50% of the time after Stealth Rock, Gligar is easily OHKOd by Hydro Pump, Slowbro is smashed by Draco Meteor and Snorlax is effortlessly 2HKOd by Focus Blast - provided you can actually hit. Umbreon is 2HKOd even with Protect recovery, assuming of course you can hit the Focus Blasts. SDef Mew is a pretty solid check, although a Sludge Bomb poison could really screw it over. Psyshock does pretty heavy damage in return, however. Meloetta is a pretty solid counter unless at least 2 layers of hazards are on the field and it is not bulky, in which case you can OHKO it with Draco Meteor. A huge number of offensive Pokemon are looking at getting 1-2HKOd for sure, with notable OHKOs being the pixies with Draco Meteor after SR and Nidoqueen with Hydro Pump, even if it is defensive. Togekiss mostly likely will not be UU, but even if it is you can handily OHKO even SDef variants almost 70% of the time after SR.
Having looked at the calcs, I'm actually seriously impressed. Good bulk, toxic immunity, a bunch of resistances and enough power to 2HKO almost every wall in the tier. Even discounting a defensive set, I know I for one will be using thie shit out of this.