I share for a friend who has a lvl 78 rogue (none of your business folks) I had been frapsing my technique with his skillbar and I got an msn message from him asking why a few of the really gg's who out gear him were calling him cheap and I showed him the vs's and he said not to use a blind in vs against some level 80s who really out gear him.
I personally think it's fair to blind in vs against warriors when their hp gets to below 20% because they tend to scream and run off, they gonna die anyways...
against mages, only if they are light and you just came out of a long stun.
priests, if they throw on a shield and duff you, and heal
and only against rogues if their hp is almost down and purple skills and bloody are cooling down, or they blind you
and then the whole, you are dropping anyone in a vs and their friend comes to help.
personally I want to know everyones standards because it's hard for someone with shell/chitin +8 and shards +8 to drop an 80 bp or 80 warrior with IN and what not..even a rogue that has in and a few +2 and 3 uniques..