I highly recommend the 5 minute breaks on the hour. You've gotta be strict about the 5 minutes, turning it into the 10-15 minute breaks people are used to really cuts into your time, but if you just think about the average attention span of a human being it really does make a lot of sense. I like to try to look outside the WoW environment for management (time, personnel, motivational, et cetera) approaches and I like the ability to build my RL general organisational skill-set in WoW.
And yeah, I find asking them about my performance invariably turns it into a dialog of compare+contrast "these are my strengths, these are your strengths, these are my weaknesses, these are your weaknesses" where it's normally so easy for people to close their mind to perceived criticism. Plus I take the PoV that the raid/guild leader should clearly be one of the strongest players to demonstrate that they deserve their role, so it's handy to have a bunch of critics there to keep you on your toes & hopefully you won't instinctively dismiss their criticism when it's done in a mutual dialog scenario =)
Edit: And I very much agree with Qujam's comment above.