>>43771438Rillaboom is currently RU. Grassy Surge will make it at least UU. The only reason I'm hesitant to say OU (and I'm talking long-term, not the obvious OU starting point and new toy syndrome effects that keep it there) is that Grassy Terrain got nerfed and Rillaboom has no secondary type to back it up defensively. A lot of Bulu's authority came Fairy letting it take on things like coverage-lacking Ash-Greninja, Garchomp, Zygarde, etc.
While I really like that Rillaboom has U-Turn to distinguish it from Bulu that now has Play Rough, which does matter
>>43771520 in not getting answered by Kommo-o and other Dragons, I'm not sure how useful U-Turn is. Who are you setting the terrain up for that relies on Grass? Unburden mons can use any terrain, Mega Sceptile isn't coming this year if at all, and Grass which is already medicore offensively got worse now that it's 1.3x. If you're doing something like Scarf or Band Rillaboom with Magnezone partner, I think that could be nice, but Hidden Power's status is unknown and Tangrowth and Scizor are back.
As a physically defensive wall, Rillaboom doesn't even wall Sand Offense well enough if the Exca is LO and/or the Ttar is Band. A bulky AV set or SpDef set or still a physdef set I could see with U-Turn, but again I don't know what that slot would be necessary for, unless you're running EQ-weak stall.
I think its best sets are going to be SD and Banded. Banded Grassy Glide could be a useful check to have to faster threats that are either frail or weak to it. Could also help against things like Crawdaunt under TR. Could very well end up OU, but I need to see all the tools we get in the DLC, this is just current speculation.