MCH is rare because its in a pretty bad spot.

For the low cost of not bringing bards better group buffs, you get to do almost-monk level damage. And if you somehow are in a group that also has a bard, you essentially become a selfish damage dealer thats further behind other damage options than you are ahead of bard.

Its also based around an Inner Release rotation with more dexterous windows, because thats SUUUUUUUUUUUUPER fun to get lined up with everything you have to line it up with.