In fairness, Frost is ridiculously strong on all M+ in PTR right now, and this is probably the most relevant it’s been since like 8.2. It can handle any affix combo reasonably to extremely well; & the flexibility of choices between FW & GF for dungeons (or sometimes, swapping between both in the same dungeon) makes it a very solid pick. For a pure DPS class it offers great role compression via Lust, a buff, Curse removals, and baiting to then invalidate many mechanics that are otherwise extreme healer checks or even fatal.
Sanguine and Necrotic are probably the most annoying affixes it has to face as these usually cause more than normal levels of kiting which lowers Blizzard uptime (so by proxy, FO uptime). However, all specs have certain affixes that soft counter them, so this isn’t necessarily a bad thing. If anything it gives more incentive to recalculate routes or comps to optimize DPS in the face of these challenges.
The ST buff is probably thrown in for raid, where it could use some help given how the fights in this tier work. The entire raid tier isn’t very ranged friendly though, and its ‘balance’ is entirely dependent on the dom shard set bonuses. Interpret that as you will