Why is the is-4 meant to be such a bad heavy tank?

Draschel: Talk to  Tasty. He loves IS4 I think it is at least better than ST-II What I don't understand is the lowered accuracy. Even with E100Buffed the dispersion stats, aim-time....but then club accuracy?  lol  Give it 180 LFP, make the UFP 160, 35 ammunition, and restore the 0.38 accuracy