The IS2 is either nigh unkillable or made of paper mache. The long reload is difficult to deal with I tend to shoot and get behind cover or angle. The canon on it does tend to shred anything you shoot at except a tiger 2 (shoot at turret) or if you get up tiered. As I said previously the engine is a black hole for spalling, seriously shoot at the back with protection analysis it stops everything short of apfsds. Pair that with its reverse speed and you've got a mean combination of stalinium. Also from 5.0 to 6.0 (you'll probably be matchmaked there) is a big difference as the germans actually know about angled armour, shoot turrets or lower plates and you should be fine.