I think this is the most fun I’ve ever had sniping in this game, very viable at OP 8
http://bl2skills.com/siren.html#055401555041050000000505510551
No specific gear needed except for snipers of course but I’ll list a few things that I recommend and why
SNIPER
Snider(my personal favourite)
Pimpernel(with converge and chain reaction the pellets usually hit more than one enemy)
Volcano(with converge the splash damage is useful)
Might wanna take a Norfleet or DPUH for FFYL
SHIELD
Cracked Sash(for casual things)
Blockade(for prolonged fights)
Flame of the Firehawk(for more AOE although more for emergencies as you shouldn’t be that close when sniping)
CLASS MOD
Legendary Binder(for boost to Reaper, Helios, Suspension and Wreck)
You could use the Legendary Cat but SMG boosts are useless for this build
RELIC
Bone of the Ancients: Corrosive/fire(depending on the situation and gun choice)
Heart of the Ancients(with sniper damage)
Stockpile relic(if you run out of sniper ammo a lot)
GRENADE
Honestly comes down to preference and situation, use your best judgement, that being said a Quasar is your best bet for crowd control.
Hope someone enjoys it as much as me