160*1.5=240
1080/2=540
540=/=240
Your calcuation for the Jagdpanzer IV's vet5 first strike damg is slightly wrong:
160*
2.5=
400
1080/2=540
540=/=
400
This + 1 KT or 2 Panzerschreck hits and a medium tank is gone (640HP)
Also notable is that the first strike basically is a guaranteed penetrating hit, even versus an IS2!
Though your point is still completely right, it's still not 50% (37% to be precisely) vs IS2.
But the Jagdpanzer is still probably the most powerful and
cost effective AT unit OKW has to offer, especially against the current call-in / medium armor spam meta (much much more efficient than the Panther).
The Jagdpanzers vet bonuses are also one of the best you can get among all OKW units (see bonuses
here) and it levels vet relatively fast. You simply have to keep it alive by all means. At vet5 it means terror for your enemies armor, also for the IS2.
I don't know why it is so heavily ignored by players and they stick to the panther. Sure Panthers are great, but also cost 30% more fuel and but in terms of doing its intended job - fighting enemy vehicles - the Jagdpanzer is a much more efficient choice (cost and DPS wise), especially in team games were you will ALWAYS have something to shoot at.
Well, just me again advertising for the Jagdpanzer IV.
It won't help against "IS2 beeing a way to overprerforming tank and coming too early" call-in meta, but it's at least something.
regards
ace