Unwarranted like the Panzerwerfer-nerf after the panzerwerfer-nerf? Or the (I hope accidental) ninja Panzerwerfer-nerf in the last patch? The unit that is stuck like that for over a year now? Relic is going to do whatever the fuck they want. 
And a mild Tiger buff isn´t going to break the game. Keep in mind it also has been constantly nerfed (HP decrease, Blitz nerf, no armor buff on vet, call in limitation to 1). It was lacking as a heavy tank, thus needed adjustment. And instead of mirroring an IS-2, it gets range.
Panzerwerfer was nerfed, so was katyusha. It wasn't very significant.
Keep in mind that relic IS buffing the panzerwerfer in the next patch.
I'm not saying its going to break the game, only that the change was not needed. Why did it need a buff? It was more effective againts infantry than the IS-2, and slightly less effective againts tanks than the IS-2. (More effective againts medium tanks thought, still)
Just because there is one allied tank in the game that it couldn't beat in a 1v1 slugfest doesn't mean it was underperforming.