that tank will decide when to go

Hell yes it is extremely rude. No one....and I mean absolutely no one needs to nor should feel the need to say "go". The tank is the leader of the group and therefore that tank will decide when to go.

Quit being so impatient. I've tanked my fair share of instances during WotLK on this toon (have since sort of retired) and everytime someone told me to "go"....well guess what? World of Warcraft(EUR) I stood there. Either I stood there or I told them "you're more than welcome to leave and find another group since you're so impatient."

I grew sick and tired of players who has the "I has ADHD, must get #1 in recount pew pew pew stand in shiney fire stuff b/c it's a buff" attitude.