Re: Massive Darkness. I'm usually wary of kickstarters, specially when they start promising more miniatures without increasing the cost. It's doubtful that a game that budgets for 75 minis can hand out 39 more without raising the price or lowering the quality (numbers may be wrong, not sure whether they are including the stretch goals in the base box details). They are CoolMini, though, they already have other successful kickstarters, so that's something in their favour. I'd sorta trust this not to blow in your face and to deliver more or less on time.
Problem is, not having an available rulebook should be a huge red flag if you care about the mechanics. I haven't been able to find one, at least, and didn't have time to go through the gameplay video (the rules one is pretty useless). My general impression is that this is another cookie-cuter dungeoncrawler that is sold on the strength of the minis alone.
Basically, do you feel like paying 120 euros for a bunch of (admittedly pretty) minis? The game, if it's any good, is a bonus.
Regarding Gloomhaven, I've seen Radho's runthrought (goddamnit, man, write a script) and I like the idea of card management and euro feeling of the game. It feels more tactical, with decisions mattering more than in MD. At least it's original, and the Legacy stuff is also cool. Haven't played Forge War (the designer's previous game), but if you have you can make some assumptions based on that.
Between the two, I'd rather pick Gloomhaven.