I personally have little use for combat healers that are dps first, healer second. I will use Holy if I can go through the cast time and not lose the tank (which depending on the tank and the pull can be a problem)

if I have time and no one is in urgent need of healing I will help with dps,

most of the time I dont trust the other healers to do the work unless I know them, so yes, if the other healer seems to only want to throw glare, I just ignore them and complain about it later, and hope to never see them in a raid in my group again. (or heal for me if I am anything other than healer lol)