The tiger will beat an IS-2 now. The tiger is now significantly better againts infantry, and better againts armor than the IS-2.
It wont affect much anyways, since IS-2 is still a very good tank..
The IS-2 got 75 more armor, the Tiger got 10 more pen. That means the IS-2 effectively has 365 armor vs the Tiger's 300 armor. 22% more armor for 22% slower reload.
The IS-2 has a 10% better chance to pen the Tiger though (63% vs 53% at max range).
So, the IS-2 deflects more shots (which negates the RoF advantage of the Tiger to some extend) and pens more often.
BUT a fight between these two tanks is decided by RNG anyway. Hard to predict which tank wins although the IS-2 got the theoretical advantage.
Regarding AI effectiveness: The IS-2 got better AoE but more scatter (it hits less often but hits hard). The IS-2's top mount MG also deals way more damage then the Tiger one.
I'd say in overall AI effectiveness they are kind of equal. Again, RNG decides how good they perform.
The pen buff makes no difference vs all Soviet/USF stock vehicles. It's only slightly better against heavy UKF vehicles and the IS-2/ISU but those vehicles have their own advantages over the Tiger.
The pen buff is absolutely fine IMO. What confuses me is the range buff.