Sniper skills are cool but hardly playable at hard levels, which regretably reduce the diversity of playstyle at end-game.

Why are they not playable in hard levels?

We aim for several seconds, we CANNOT DO ANYTHING during this period, then the damage is dealt to single enemy——and the damage is low ! Often the shot only scratches that one enemy, in hard level. 

 (because no vulnerability was there, we spent the time just standing there and aiming, rather than fast-hit the enemy and apply vulnerability debuffs, as we would do with other weapons)

The idea that making sniper skill an instant killer may sound greedy, but it is actually fair.  

After all, if other fast-hitting weapons could kill a boss and all of its  retinue in 5-15 seconds (with -99% damage dealt), what's so wrong if a sniper "instant kill" that boss after 10 seconds of aiming? 

Just make the killing time matchable (like, the instat kill chance increase with aiming time and/or focus/enrage/berserk state).  It is easy to implement , and it is fair.

It could also revive the enchants like "explosion on single target one-hit kill ", which are fun but dead at hard levels.

So please consider this and make sniper revive, thanks!