Personally, the reason I queue into Solo Rumble is that I enjoy not having to find a team and coordinate times to play with them. I do not expect to go into Solo Rumble expecting any amount of teamwork or coordination aside from “focus weakest target”. So if my team for that round is doing bad, it’s not something I take to heart because I never expected them to be good in the first place I go into Solo to hone my skills and challenge myself to win and be that deciding factor that tilts the scales in our favor. Sure, there’s plenty of times that I nearly clutch the game all on my own and nobody capitalizes off my plays to snatch that win but that just means go again and try again. Don’t let yourselves get frustrated with teamwork, just focus on your own skills and hone them so that you can carry any team you’re on.
I feel like rumble is easily solod by most champions that can effectively kite and whirtle him down from range. The most important thing is to avoid forcing fights in compact spaces post level 6 to avoid his ultimate.