Haha I am glad that i was able to help you guys out , when I saw the post i just instantly knew i had to post the fix that I had found because I know how much this drove me crazy and I always felt like i was getting screwed out of both the xp for mobs but mainly the xp for finishing the fate since it is based on your contribution.

If only they counted me hitting the targeting button a million times trying to target the mob as actual contribution! haha

As for the up and down keys for healing, I agree they are priceless.
But the same goes for the right and left keys on the D-Pad for dps, because when you have your weapon out, after you try and target a mob you can spam the left and right keys and it will scroll through the mobs from closest to furthest so that way you can target the right one for attacking.

It is actually a decent system once you get the hang of it