I can definitely see a 'witchfire' type spell being a kind of basic ranged attack for each psychic class of the races. Lightning being the most prominent one used by the Eldar. Farseers could almost be considered the most iconic of the Eldar paths so i'm sure the devs have put a lot of thought into their creation and implementation in to the game. Given the nature of the Farseer and Warlock spells (such as Guide, Doom, Fortune, Embolden, ext.) I can see them passing out buffs left and right. This could also help give Eldar that 'elite' feel when everyone in a squad is buffed to the teeth.