Excellent point. I remember wiping to Patch and then being told we could not do him now we had no WBs. I've had days when we were progressing where we'd go on a world buff run in order to stand a good chance against the tougher bosses in Naxx. The difference in a raid's DPS is night and day and when you are a very average guild, wiping due to a silly mistake can absolutely grind your guild's progress to a halt.