I've been trying not to say too much, since others are enjoying this mode, but seriously this is a bad mode, IMHO. Where you see excitement in racing to kill the boss before he can one-shot you, I see a cheap trick where the options I have spent the last years slowly developing complimentary teams are tossed on the trash ... no longer do I have the option to decide if I want to deploy a team with a Silence approach, or steal his mana, focus him down with one of the many approaches (like triple against his color, true damage, etc.). All I can do is try to brute force beat him down, and I don't believe those who don't purchase the anti-boss Xiong Mao troop out of their gem shop will have much success, at all.
Not to mention that traitstones are a valuable strategic resource, at least they are at my level. I've had so little success in trying to farm them that my understanding is the drop rate for Arcane ones is so low that it's not reasonable for me to attempt to farm them. For these new troops to roll into town and ask me to blow my traitstones on them is ridiculous.
Of course, I may be missing something.
Having said all that, the rewards are not so lucrative that I feel like I have to either throw money at it or quit the game entirely in frustration. It's just another mode/option, play it until it's no longer fun, then play a different mode or play a different game, or go read a book.
One of the things that I have learned from this discussion, is that I do need to learn about the Hero classes and developing my Hero. When they did the big Hero changes, I never explored them but rather kept my focus on developing my troops and teams.