RE: Archaludon, as the Walking Wake suspect showed, if a mon is only problematic on a specific archetype, then it really does matter how good that archetype is.
At the time of its test, Wake was clearly too good on sun teams, but sun teams were otherwise sub-par, so while "Wake on Sun" was an overpowered mon, "Sun with Wake" was not an overpowered team - and so Wake lived.
"Arch on Rain" is arguably too good for a single mon, but what really makes it the next suspect test is that rain is otherwise very solid, so "Rain with Arch" is utterly dominating at high levels. Now, maybe this'll change as the meta adapts - that's one of the reasons for an extended suspect test, so that adaptations have a chance to develop - but if those adaptations are all 'rain exclusive' and serve little other purpose, then that's unhealthy. If they're otherwise-good mons seeing greater use (IE, DLC1 Ogerpon-W) then that's fine.
This also means that, yes, other nerfs to rain that end up knocking "Rain with Arch" down would be a workable solution, though Finch has made it clear that Archaludon itself is being suspected.