I think you need to be careful otherwise you're just making underutilized doctrines like mobile defence worse. So a nerf to PT is unwise.
It definitely should not be in doctrines with tigers though, the tiger is already the best heavy. Pixie dust smoke is just the icing on the cake. It's like giving the IS-2 mark target, sure mark target is balanced but giving it to an IS-2 just screws with heavy balance.
Yes some commander abilities combination should not be available. Then these abilities will be easier to balance.