Buff Nascent Flash

[Zyneste]

I never use this feature because I just hit down on my directional pad twice for the next tank, theoretically if that's how it works, you are attacking the boss, you L3 and it targets tank, you use skill and press L3 again and it goes back to the original target?

Yep thats how it works. Typically though, ill just use the DPad to target the tank THEN use Assist (L3) to retarget to boss since sometimes they are near impossible to retarget. This way its quick and easy. Its an especially helpful on a healer who has to bounce back and forth.