Depends on raid time. Our particular raid only does 3 hours so there is no actual break in the middle of the raid time, but ive seen anywhere from 5 minutes to long 15 minutes break (only seen 15 minutes if raid time excedes 3 hours though).
No breaks in most raids (3 x 3 hours / week). But you can fast take a drink between bosses or after a wipe. If most of the raiders ask for a break or we kill bosses faster than normal we get a break for 5 min.
Usually a 7 minute break halfway thru our 3 hour raid. If someone needs a quick bio they can just ask for a rezz instead of running back as long as it doesn't become a consistent thing to do out of laziness.
We just randomly afk.
You can have 1-3 people go afk while clearing trash if people just communicate so we still have enough tanks/healers and dps there to not to wipe.
We rarely take any normal breaks. I think it only happens if we are wiping 2hours+ on the same boss or something.
Well I'm not raiding at the minute but used to raid 3 hours 3-4 times per week, we used to take a 10 minute break at the half way mark, but if anyone needed to go to the bathroom in between that was fine as long as they were only a couple of minutes whilst we were doing trash or running back and we'd often use that break to watch a strategy video if we were struggling on something.