I'm the shortest Miqo'te you can possibly choose (literally the only way to be any shorter would be a lalafell) and I'm a lvl 38 paladin tank. The only time I have problems targeting is if I'm zoomed in too close (easily fixed by just zooming out) especially if the mob is really big (looking at you Cancer you bastard crab) Though sometimes my targeting gets screwy like some how i targeted myself but that has nothing to do with race or height issues and more just retardedness on the user (ie myself)

... and on a side note ... god I love this game :3