All of the Y1 exotics should be underpowered for TTK endgame. They should be fine to get you started in TTK and slowly become underpowered so that you grind for newer gear to make the midgame easier, then you struggle a little on the endgame with that newer gear in attempts to obtain the best possible gear to make the endgame easier. Letting Y1 weaponry be the best possible option for TTK endgame is asinine and makes grinding for anything new pointless.