My bad, you are actually right, it shows 1% right now. It was 100% yesterday, even after I cleared for the first time (and I got a legendary sword). 48H cooldown, so I can't retry.
Well, I missed the lvl 50, and it's because you have only one try per 24H. When I tried, I got someone randomly killed and couldn't clear it again. That's all. Nothing far fetched.
Never said bosses were the real danger here. Micah as an enemy is a bitch (her aoe deals large damage with ridiculous aoe), and the archer guy is also crazy strong. Bosses are not that hard, indeed.
Yes, I know, the lvl 60 boss is impossible without that particularity.
You wont kill bosses quick enough with 3 ranged. That's the main problem. Even if you can avoid deaths, there is a timer, and it's tight when you are progressing through the game. The start is basically the same with 2 melee. Just put them on different side so you know who the boss is focusing, and hold the target. You will even spread the basic attack damage (making the heal skill more effective).