Berserk and TF are mutually exclusive--using Berserk removes the TF buff, and you can't activate TF while Berserk is up. You used to be able to some number of patches ago, but not for awhile.
One thing worth mentioning, is it's best to time TF when energy is low, and Berserk when you've got fairly high energy; all while taking Berserk's duration into account for TF's cooldown, so that you don't waste time with TF off-cooldown during a berserk. I usually pop TF for my bleeds, wait a tick for regen after TF is over, and then hit Berserk.