Your guild leader has an archaic mindset that's so wrong it hurts my face.
First off, the set bonus makes it free. It's free. Free. Second off, prot healing scales insanely with vengeance and stacks of Bastion of Glory. Your healing is part of your mitigation, if it wasn't, it wouldn't be tied to your mastery.
The more you heal yourself with your insanely powerful self heals, the more the healers can focus on raid healing, dispelling, or whatever the hell healers do.
Lets look at it closer.
You have a choice. You're sitting at 5 stacks of Bastion of Glory and your whole raid just took raid damage, and everyone is sitting at about 50-65% life. Would you rather spend 3 holy power to reduce incoming physical damage to yourself by 50% for 3 seconds, of completely heal the damage you've taken and put a super powered 30 second hot on yourself that will auto nullify minor damage for 30 seconds?
The mindset of DPS are only to DPS, tanks only hold aggro, and healers heal is ridiculously outdated. You do what you can, when you can, however you can. If I, as a Ret Paladin, can throw a life saving SH Flash of Light to save a healer at 10%, I'm gonna do it. Screw my DPS. I want to kill the boss.
TLDR; Your GL is super wrong.
Edited by Andhar on 10/28/2013 8:52 AM PDT