The Sub at your local has been setting up the clone in the same spot every time and intentionally armor breaking wake up attacks with b2? I'll take your word for it, but that's a random Sub at a local. No major tournament player used the tech and no one discussed it in the Sub forum unless you can prove me otherwise, and even if they did, that wouldn't change the fact that Sub Zero is top tier because of it. And you don't have to land a 50/50 to set up the clone, all you have to do is use a f4, f42, b12, 123, or d4 into ice clone on block close to or in the corner and you've got it setup. The only truly safe one on block is f4 but not all characters can punish the other strings, f4 is still easy to land, and you can bait a punish with the EX clone, so yeah, you do not need to land a 50/50 to set up shatter combos, you just need to get them close to the corner and get the clone out by any means. You can also get it out safely by ending midscreen combos with 112, which sets up the shatter combos in the corner if you're the right distance from it. Shatter combos are constant difference makers, especially if you have your opponent already in the corner at the start of the next round, just get the clone out and your opponent is stuck in the corner ready to eat those shatters.
Sub's damage could be normalized by increasing the scaling on the clone shatter, but nerfing f12's damage and b2's damage are more logical. Sub should have to sacrifice significant damage to get the clone out safely. Currently using f12 instead of 123 slide to end corner combos only decreases their damage by 2%. That's not significant enough for how huge of a reward getting a safe clone out after a combo is. Plus making f12 9% instead of 12% would make 112 the go to hard knockdown string for unbreakable to use for safe ice aura set ups, since f12 does slightly more damage and gives more advantage, making 112 less useful in general. As for making b2 7% damage instead of 9%, currently Sub Zero can get a 38% combo off a raw overhead without the use of a clone shatter or meter, 36% if you want the safe clone setup. That's too much considering how high tier he is with his armor breaking tech. Simply increasing scaling on the clone shatter would not effect these 2 issues, which is why I don't prefer it.
Lastly, b2 from behind the clone in the corner might not be completely safe, but it requires a 12 frame or faster forward advancing EX reversal attack to punish it, which few characters have, and even if they do have it, unless it's a launcher it's not really worth it.