Talking about the gameplay design here. While I’ve never been a particular fan of the whole ‘NG+’ kind of thing in general due to poor balance and such, this looks like an especially bad version, hastily cobbled together, with the stats and numbers just scaled somehow to ‘OVER 9000’ (while distinctive features of bosses are not, by the way). This might sound or appear ‘exciting’ to some especially… hyperactive types, but if you look at it, those boss battles resemble more of a war of big stats and brute force than puzzles or problems to be solved in specific ways. We’ve had some badly-designed bounties with this kind of problem (The Sunken City bunch or the ‘Chess Event’, where one of the most effective ways to solve it, probably, is just to burn everything with fire — blunt and straightforward, no nuance, subtlety or clever strategy required, which, apparently, is HS’s take on the theme of chess 
), the whole ‘boss rush’ seems to take it to the extreme.
Sure, it might work as a renown sink, it might even entice some to ‘whale’ in order to do a LEVEL 9000 BOSS RUSH, considering how the cost of ‘mythic’ upgrades goes up in an arithmetic progression after a certain point, just for the ‘achievement’ — but what I’m talking about is how I’m not convinced that this is the kind of fun gameplay which Mercs fans would appreciate. It could have been a ‘puzzle rush’ (was it chess.com that has this kind of entertainment?), instead, it looks like a ‘smashing with big stats rush’, as far as I can tell right now. Could I be missing something?