All I do is to rotate my camera angle up mantaining my desired target inside the view before clicking tab. Sometimes it's annoying since we have combat mechanics to work out and AoEs to avoid...

using mouse button is infuriating as well when someone (or another mob or minion) pass in front of the target in the very same moment that you mouse click the target.

They should use the same system we see in FFXII. There the targeting is far way easier: the first target is always what is rightly in front of you and circles from nearest to fartest. To reach left or right sides you have to keep pressing the targeting button or by front facing the desired target first with your char.

I don't know for sure, but it seems that the "cone" option do exactly this. But i need to investigate more about it...