I tried something yesterday, doing pvp all day long :

i bind "target nearest ennemy" to G, it works, then i use tab and it switch between the other close ennemies.

(i bind "F" to "face the target". It's a great help when i heal in pvp to quickly find out in which direction the ally you clicked on is.
And i use ctrl+tab to cycle between close allies, it work well like in Swtor)