its turret isn't hard to pen, only 100 thickness on sides and you can see the sides from the front. If he looks around much at all you can pen his turret from the front. The sides of the hull are easy to pen too and it is very slow, with poor acceleration, and it has bad turret traverse. It also has pretty low dps. Its dps is worse than the tiger1. Most heavies should be able to pen the lower plate I think especially if the tiger is going uphill or if you are on low ground. You can pen the turret cap also though it is small.
Anything that can pen the lower plate can pen it easy because it is a big target.
So, in a nutshell, if you can't pen the lower plate, and he doesn't look around much, just maneuver to his side. I don't really consider tiger2 threatening, I am surprised a unicum thinks it is almost OP.