Difficulty is relative, which is why it should never be used for balance. Things like utility should be.
I find MCH harder to play than SMN, RDM, and NIN. (You can call me crazy, but I remember the Mudras super easy with little stories in my head like "The cunning of Man" to know which one lets me cast Trick in combat and knowing that all that matters for Mudras is if they're 2 or 3 long and what the LAST one is - the first 1/2 don't matter - so I just get in a groove on NIN that I can't do as well with MCH). BLM is arguably one of the easiest DPS Jobs in the game in terms of rotation, it's just tricky to work that into boss mechanics that require movement. SAM is also pretty straighforward once you get it, making it pretty easy, too. And let's be real, with giant hitboxes and even omni-directional wall bosses and short CD 2 charge True North, it's not like Melee is starving for uptime or having difficulty with positionals these days. And most of their positionals have been either removed or had the damage loss by missing them minimized.
Difficulty is relative.
The problem is that you can't have a "selfish DPS" in a role that has a damage penalty. MCH should either do as much damage as at least RPR or something, OR is should offer utility more comparable to DNC and BRD.
Imagine if you had a healer that had only Medica and Cure 1, but was a "selfish DPS" and did 500 more dps than the other healers. No one would take it to any raid. You'd be better off bringing a PLD or RDM at that point since they'd do comparable healing and even the PLD would be bringing more damage.
I don't know what it needs, but one of the two - more damage or more utility/buffs. I've seen some people propose a combat raise (which would be a stealth buff to BLM since it would mean if you have a MCH you can possibly pass on a RDM/SMN), but I honestly don't know.