dunno why it bothers you, I never drop a guard... it's tanks decision who he wants to guard. if he guards you, it can only mean, he's not sure who will draw aggro from him more, and preffers to put guard atleast on one person, then on noone.
Don't tell tank how to tank and he won't tell you how to heal.
that's what I do on my tank, if dps are not super geared, or equally good geared, I preffer to start with guard on healer, as I don't know how dps will act, and then change guard accordingly to situation.
Yup yup. I don't guard dps unless I'm ordered to on an op. If you are a dps you need to learn what to attack and how not to take excessive damage. If you are drawing agro on hard-hitting mobs you are doing it wrong.
Also if you do heals and you are not worried about catching too much agro then you simply are not healing enough, your area heals will generate life-threatening agro at times but they offer the best healing bang for the buck and you should use them often.