I'm hoping this isn't intentional since it wasn't in the patch notes but seeing as melee builds took a big hit with the One-Two punch nerfs I'm not sure. Technically its not that they don't stack, the benefit is just a damage increase of less than 1%. Including One-Two punch, meleeing a large blocker in gambit dealt 360 damage. Meleeing a frozen large blocker under the same circumstances dealt 361 damage. I've tested this multiple times so I know its not a fluke. As a sidenote, meleeing a frozen large blocker without One-Two punch dealt 396 damage, so it's now detrimental to use the perk against frozen targets. I know its not a game-breaking issue or anything like that but the combo was really useful for melee builds in higher end content, since neither one-two punch nor stasis alone pack enough power to deal with beefy majors like Knights and Captains.