Hi, OP! I've only done The Burn one time, and in itself, Misty is harder than the other bosses in the dungeon for sure. But in context, when more people are used to it (and I imagine a lot of people are by now), and outgear it, it'll just become another dungeon that pops up every now and again. Pair it with Saint Mocianne's Hard Mode and run the lvl 70 Expert roulette, and you will get used to it, and what was a hard thing will no longer be so. I'll certainly be back at that roulette this evening, Chaos dependant, because this is fully how I want to tackle lessening The Burn (St. Mo's HM was relaxing in comparison, but I have no idea why!). I don't have the lengthy gameplay experience of a lot of other posters here, but this seems the best way to tackle the place.
I don't mind saying, it usually takes me at least 3 passes at a dungeon/boss to fully understand everything that's going on - for example, I only picked up Swallow's Compass recently, and whilst most of it's fairly sensible and not too hard, that second boss? My brain has a hard time translating his arm movements for sure! I end up sticking to someone I hope is less borked in the brain than I am for that and the third time I ran it recently, I only got hit once by a stupid arm thing, and didn't die or make too much of a mess the rest of the fight! It might seem nooblike to others (and truly is), but I'm happy with my progress! Next time, I really have to make an effort not to get hit with his stupid arms at all. I have to say, I have been That Bard In Narnia (surely this has to be trademarked for future reference?), so that's something else I need to be mindful of and work on! I never want to stress healers if I can help it.
Anyway, that's all it is: keeping your gear up to date, practising, taking advice and just getting stuck in. Also, I find running all this stuff with someone you know makes it better, too (if you're not already doing that). Everything new will always seem hard(er), but just keep at it, and at some point, you won't even be thinking about how difficult it seemed.
And I agree: Misty is like Isgebind. I used to be terrified of Isgebind, you know. I was also terrified of just going in any dungeon. Sometimes, you just have to face up to those scary things head-on, and after a while, they're really not all that scary any more.