What makes Mistweaver Monk a bad healer?

So I main Resto Druid and have gotten my KSM on it (pugs only) and wanted to get it on a different healer. I love my Mistweaver Monk, but why is it listed as an 'F' tier healer? It has tons of utility and I have healed up to +7 keys in time with no deaths that I can take credit for. It has more damage at 380 ilvl than my 403 resto druid main. I am running into the problem where I have to run my own keys because I can't get invited into even low pug keys. I have no problems in my own runs or runs with friends. I run all the enchants and embellishments and use all of the consumables that I am supposed to. I even use the brez engi cuffs and drums when necessary. I think all of my bases are covered. I still plan on pushing to KSM on him, even though it may take some time. Yes, I run my own keys. So what is it that makes the Mistweaver monk have such a low image in the mythic community?