Cranswitch, put more vit in your build and a sight clip.
Snipers have a decent HP modifier, 0.85, so with a medium amount of vit and a cranial they should be able to tank a hit off.
basically, put sight up, lay a few traps down, always have a cranial shield on and when you get SB'd, tag to bow (use /bm if you didn't already) and start DS'ing.
Try to read what element your enemy uses, it's always handy to have evil druid, ghostring (if you have acces to it), and the 3 elements, pasana, dokebi, swordfish.. fire wind and water respectively.
As a sniper, I can't stress this enough, if you're not DS'ing or attacking, equip your goddamn cranial.