Who do you bring to the raid? Is it the player or the character? What would you say if a character is played by someone not owning the character, and there were other players benched from the raid? How would you react if the switch of player was not communicated, not even to the raid leader? Is it OK for someone else to play the character for lets say one hour into the raid until the right player is available? For me it is obviously the player you bring in 99% of the cases. The only exception I can see is if a specific character is really for the raid to be continued. I would also say that it seems very self centred to "sneak" into a raid like that when there are other players waiting in line.
Sorry for another rant post, but some things really annoys me (and no, I was personally not directly a victim to this).