So, I've been giving it some thought and honestly, while I can't speak intelligently on BRD (BRD players will have to comment on their class), MCH doesn't really feel like a support class. Pretty much all of our utility skills are short lasting, on long cooldowns and are entirely situational. I consider us less a support class and more an "oh ****" class. Everything we have is situational at best and isn't truly supporting the party. When things hit the fan, we're useful. When not, we're a burden. That's NOT how support is supposed to be, so I've come up with a few suggestions to make MCH real support and not a class that's just brought along for progression and then dropped when they aren't needed anymore.
MP/TP Regen: Give the turrets back their attacks, remove the 15% damage loss from BRD. Reason: We already have lower damage due to lower weapon damage. No need to punish us again for doing the job we're supposed to be doing.
Physical/Magical Vulnerability: Make it more like Hot Shot. Something that needs to be refreshed or even uses MP, but lets it stay up as a permanent buff. Reason: There are a few classes that can keep up a permanent debuff of 10% against slashing/piercing. No reason why we, as a support class, shouldn't be able to give 5% to the whole party for physical or magical all the time. This would help make up for the lower dps we do.
Dismantle/Rend Mind: Same as above. Reason: Helps ease the burden on the healers throughout the fight instead of just on situational tank busters. This makes it useful much more than the 10 seconds we can do every 90 seconds.
Obviously, they'd have to balance these. My suggestion would be to possibly have them be different "turret stances" or something like that where they drain mana. They could even be various "promotions"-- or, Knight Promotion for damage reduction, Queen promotion for damage buff and King promotion for regen. You can only have one stance up at a time, either providing a damage boost, damage reduction or tp/mp regen. We may have to switch them depending on the situation. This would allow us to really support the party at all times and justify the lower dps we have in all content, not just end game raiding content. I'll gladly take a hit to dps like we have now if I felt like I was always bringing something to the party through all content and not just holding the group back.