I don't think you can see it, but I believe the default key binding Alt + T will target your target's target.

Thanks for the responses guys. I was always partial for creating an assist macro and just changing the name of whoever the tank was in the group I was in. Guess I'll just have to get use to the extra key click for target of target.

Is there no way to create a macro in this game? I'm sure it's been asked before but I can't seem to search the forums for it (I hope they bring the search function back soon).