Actually, Ho-oh in the rain is quite underrated. Like Rain Volc in OU, Ho-oh ends up a lot of potential to a lot of rain teams, like Ferrothorn, Latias, Grass Arceus, Fighting Arceus, as well as giving you a huge weapon to use against sun teams. Brave Bird hits most things you want to hit, while Sacred Fire is still useful enough against the threats you want it to check (Ferrothorn, as well as 50% burn). While yes, Ho-oh is a lot less effective and harder to abuse on a rain team, you shouldn't get into the mentality that "Oh, I'm running a rain team, therefore I'm writing Ho-oh off immediately". Ho-oh is not something you'd want to abuse on a rain team, but is still really good to glue together some weaknesses you may be running into.