I knew I was forgetting someone... I feel Espathra would still be pretty stupid, but I'll give you that one. Palafin I'm less sure of, as it isn't even the most fringe position to argue it would be okay in *this* Tera metagame. I'm not sure I agree with the notion, but I also don't entirely agree Tera being a factor to be that noteworthy, as a generational mechanic which affects every mon will naturally lean top heavy.You forgot about Espathra, which was only banned 'cause Tera Blast let it break through Steel-type Pokemon. A lot of Palafin's brokenness was also derived from Tera, and it would be so much easier to deal with without the generational mechanic. I agree with your point overall though that the vast majority of the mons banned from OU would be broken regardless of Tera.
Well, for one, losing Multiscale's insane defensive utility is precisely part of the opportunity cost of running Band for the immediate damage. A Boots nite could likely live any of Moon's +1 options with Multiscale in tact, and you can now either use that turn to deal safer midground chip, or as was ignored before, Encore, a move meant to handle the bevy of setup sweepers. This Roaring Moon is also now Ghost type, leaving it open to an immediate revenge kill from our royal friend.I'll give you another example. I got my choice band espeed dnite and I use it to revenge kill a roaring moon. It pulls out a random tera ghost and gets another free dragon dance. What else was I supposed to do?
Completely contextless scenarios against a setup sweeper are not as to your point as you'd like them to be, as there is more counterplay to these threats than you imagine.