I would tell your RL to go talk to any other RL on the server and ask them about their disc priest. Where they are etc. Also I would try and explain that you could improve your HPS but people would start taking a lot more damage and it would be like an arcane Mage spamming frostfire bolt.
That or on a hard fight wisper your RL before that you are going to use more heals instead of shields. Make sure he pays attention to the difference. Then watch as people die, or at least the content becomes harder. Would suck for the raid but sometimes you have to prove that what you are doing is important even if it is hard to notice.