How good is the Hereafter? How often does the blindness proc on it?
Hearafter is one of those weapons that are solid and nice to have, but not must have. As an exotic, it has a hard time competing with Black Spindle, exotic swords and many exotic primaries. As a SniperR, it has a hard time competing with Black Spindle and the abundant choices of legendaries (raid sniper, 1000 yard, snipers available at Gunsmith, etc)
Considering Xur is trolling us with the brutal 280 attack value, and the ridiculous 23 coin price, it is very hard for me to recommend "buy". With that kind of money you are better off getting 15 3ofCs, which should produce 2-3 exotic engrams that can end up with 290 or 310.
That said, if you are still swimming in coins, then it is a no-regret purchase.
Hereafter is a good sniper if you really don't want any other exotic for PvP. I can't really see another reason. The blinding does proc quite often though. It has the potency to be a very good tool if there will be any sort of challenge where you can't die and have no health regen or something. Anything with loads of shooting adds/ultra's and no bullet sponge boss will give it a place to shine. Whether that day comes, I don't know.