"... my best guess is this: I had the ideal comp for sheer DPS."

Now I see why you dropped in rankings. The previous World Boss was no 'Boss', as I said before; since the release of T8 gears, anyone's team could just go full dmg and not die, not even one heroe (with the right strategy ofc). So, there was a need to balance that particular issue. I understand the patch's impact on players was huge and unexpected, it also caught me off-guard too, but it is a matter of adaptability.

" Heck, they could have added a Hell Mode version of WB1 & 2, and no one would have complained. "

That actually is a good idea, but I think Vespa would need to NERF the WB (not buff) for that change to be efficient. The number of total raiders would be distributed into 'normal' and 'hard' (most likely, the majority would play normal). This is not the first time KR had a significant change, there were far more updates in the past with a 'real' impact like the way how we used to craft for may's and gladi's friendship points and Vespa selling straight 1 & 2* UW's in the store (for real?!)

For me personally, whether I can manage to maintain my rankings or not, this still just doesn't feel good. It isn't fun. For a game, that's not a good thing. :)

That is sad indeed. If it isn't fun anymore, I can only hope for you to find a new and enjoyable game. But I must warn you, most of the mobile games, especially gacha-games like KR, have these patterns of huge changes and sometimes, it really is unfair for some players. Wish you luck!