What you have said about being unpredictable is almost entirely false because no matter which way you look at it, he has a terrible movepool. There are very few moves that good ol' Blacky can run successfully, and nearly all of them are resisted by the current common walls (Mostly Ferrothorn).
Ferrothorn can be 2HKO'd by Ice beam from the specially based mixed set. Kyurem, although it has a lacking movepool, has all the moves it needs to become a huge threat to any team. Notable examples include: Dclaw/Outrage (obviously), Fusion Bolt (hits bulky waters well), Ice beam (good STAB to beat things like Skarmory and Ferrothorn), Earth Power (perfect coverage with ice beam besides surskit), and HP (HP is broken, IMO). What I mean by 'unpredictability' is, do you switch in your Skarm to take a banded outrage, try to break his subs, or switch to your chansey to try to wall his sub+3 attacks set?
You say that his sub set is terrifying against stall teams, and I'll agree, especially with Hone Claws. It is. However that's not so much a problem with Kyurem-B as it is with the nature of Substitute itself. I'm bringing back Haxorus from my first post for this example here. If this Haxorus could get a sub off against a full stall team, he could just DD to hell and back and kill everyone. Same goes for almost every mon with access to Substitute and a boosting move. If you have a Pokemon that can do ANY SE damage at all with an even moderate offensive and speed stat, you WILL be able to break that sub as soon as he uses it, because remember: Kyurem-B isn't fast compared to popular guys like Garchomp and Salamence.
The sub set IS hard to deal with for stall teams, I'll agree. But you could say that about ANY pokemon and it would be true.
The difference between Kyube and Haxorus is the huge bulk difference. Kyube has higher HP, Defense, and SpD. It also retains some of the useful resistances, such as water, grass, and electric. However, beacause of his insane bulk, he can set up on bulky grasses (HP Ice won't do enough, neither will HP Fire), waters, and more. All these pokemon are staples on defensive teams, especially Celebi, Jellicent, and more.
28 SpA Amoonguss Hidden Power Ice vs. 4 HP / 0 SpD Haxorus: 124-146 (42.17 - 49.65%) -- guaranteed 3HKO
28 SpA Amoonguss Hidden Power Ice vs. 56 HP / 0 SpD Kyurem-B: 50-59 (12.34 - 14.56%) -- 9HKO at best
0 SpA Jellicent Shadow Ball vs. 56 HP / 0 SpD Kyurem-B: 84-99 (20.74 - 24.44%) -- possible 6HKO
0 SpA Jellicent Shadow Ball vs. 4 HP / 0 SpD Haxorus: 102-120 (34.69 - 40.81%) -- guaranteed 3HKO
Etc
Also, another huge difference between Kyube and your example Sub+DD Haxorus, is that you get a free switch to, say, skarmory (note that this is just an example counter), and you can WW him for free, while you avoid the 2HKO, or just BB, or some other stuff. Whereas with Kyube, there is no safe switch in, as Skarm will get 2HKOd by Ice beam.
I say ban