Honestly, this kind of thing would get me playing Destiny a whole lot more. If I could guarantee myself some Etheric Light this way, I'd cap at least Vanguard marks every single week on at least one character if not three. I know you've got a shot at getting them from PoE at higher levels, and there's even a chance at it dropping in Nightfall, but I'll take a for-sure option that's slower every day of the week over a random possibility.