Brummbar got 50% deflection damage.
Certain legless reptile would argue here, as he was in the past, that it can be used to kill tanks.
..and certain erect creatures can argue that the projectile speed in this case completely disqualifies it as a tank hunter.
Hint: multiple soviet units have role duality, because its a faction theme together with 6 man squads, but these dual role units do not perform as well as specialists of other factions, that goes for ISU AT vs ele and jt, that goes for ZiS AT and that goes for SU-76 AT compared to all of their counterparts.
This is actually the essence of the probem - many patches changed performace of those units to being absolutely on par with the specalist units. They still, however, retained their dual purpse funcionality and larger crews (ZiS). I wouldn't change that but would simply make them more expensive or add more punch to specialit units such as pak, for example.
There isn't really any problem, just a bunch of low rank players who rush to balance forums the moment they think they lost to 1 unit and we never know the full story, because they always go "trust me bro" and some people take their words as it was a word of God himself.
Yes and no - there are a lot of low ranked players complaining but it works both ways. I feel that noobies are simply sometimes right. Seasoned players just get used to things and stop noticing certain things. Of course, sometimes it can be utter nonsense, just like You say.
ISU was balanced long time ago, since that time units it faces only got stronger and more cost efficient.
If you have problems with ISU today, that's "you" problem, post a replay and we'll help you get solution.
The fact that things can be dealt with doesn't always mean they are right.