Q:
Is there a "show target of target" feature?
If you are in a group you can put do this with Ctrl+T a target then others just have to press T to assist you.
If you mean you want to see who mobs are targeting, no there is not any way to do that. This game is not like those traditional tab target games, it functions more like the action combat games. You just have to watch the mobs and what they are doing in order to know when to dodge/move away.
If it looks like you might get hit, move.
Even if the mob is targeting someone else, if you are in the way you are going to take the hit.