Sniper was the default solo mid pick back in 04? or 05, he has insane range, best attack animation in game, headshot is free MKB, but he is slow, has no health, no escape mechanism so he kinda fell out of grace as metagame evolved (then came orbwalking era and Silencer's glory days, then MYM.Merlini and his legendary Zeus as i recall). Sadly, Sniper doesn't offer anything than damage, and that's easy to come by in dota, while being easy to gank (morph was op because he was unkillable carry, not because of his damage potential).
On the other hand, how would you all feel if items were nerfed in power a bit? In my opinion, we see same heroes in metagame because any holes in your team can be easily plugged by items, maybe we would see more dynamic picking because you'd need to proper counter enemy's team.