If anything breaks the "flow" of MCH, it's literally the heat gauge itself.
Ideally, you overheat for 10% extra damage on demand, preferrably lining it up with Wildfire and utilizing certain skills to manage ideal heat ranges besides.
What actually happens is a frequent start-stop micro-management of the gauge. Don't use your reloads under 50 heat. Don't overheat without the utilities to ramp back up as needed or it's a DPS loss. Manage ideal heat ranges (now impossible anywhere between 52 and 62. Reloads alone simply won't prevent it). The slightest mistake is costly, and mechanical interferrence (a la stuns, extreme caution mechanics, damage debuffs, etc.) can completely ruin Wildfire, and while that's always been a concern, combining that with overheating makes missed Wildfires even more punishing.
In BRD's case, there's almost no time you'd ever hesitate to use a skill. No worry of possible penalties for using what you've got. If you got it, use it, and keep that damage rolling. Songs are practically autopilot support on fairly short cooldowns, which you'll be rotating through anyways, thus keeping up the passive crit bonus, and most song mechanics working off your DoT ticks. Let me repeat that: Working off your DoT ticks. MCH currently has little that works together, and many elements that can work against each other (i.e. reloading under 50 heat stopping/slowing down heat generation, lengthy cooldowns on essential skills). As a 60 BRD, I've hit a Pitch Perfect crit nearly on par with Wildfire at 70. This hardly makes MCH unplayable, and I very much still love the job, but it really does highlight the disparity between the two:
BRD: passive party support through songs, ability procs/augments between songs, simplified DoT management allowing for constant damage uptime
MCH: conflicting skills, constant micro management to manage Heat gauge (less for optimal range, but more for prevention of poorly timed Overheat so as to minimize the damage penalties after) leads to awkward stops in execution, a full 10 levels of missing essential Heat gauge management for anyone between 52 and 62, and poorly implemented changes to things that worked fine as they were previously.
MCH currently works harder to achieve less and that's just not okay.