Bastila protection up from leader ability doesn't give jedi bonus damage/tenacit

It looks like Ezra has one dot from Vader. He and Old Ben both have offense down and crit chance down, which smells of Tarkin...but we can't tell because your screen shot is with one enemy left.

Rebels cannot resist Tarkin's debuffs, so it wouldn't matter how much tenacity they have. The fact that more of Vader's debuffs aren't present shows that the tenacity boost most likely IS working.