tl;dr: When to focus on weaker rosters (to make them passable) vs stronger ones (to bypass having to use weaker rosters)?

Wondering at what point I should stop caring about off-elements and just focus on select few. While not all of my comps have full SSR roster, the ones that don't mirror the ones that do (full water roster, no fire roster etc). Because of this, I started focusing a bit more on my weaker teams, so that I could always have element advantage, but some of my comps are just bad to the point where even if I SL everything to 20 not sure if it would matter for some of the harder content now. Can currently clear GO (the one that I'm assuming is ending now, Chrom - Dullahan one) and AQ5 with any element which I'm happy about, but feel like I'm hitting that plateau quickly while some of my better comps haven't been touched in a long while, as they haven't needed as much help. I really want to be able to solo all the elemental Ult raids however, and still can't for everything not fire or thunder, as my water and wind comps are by far the best and those fights are easier.

Fire, Lightning, and Light don't have full SSR comps if that makes any difference. SSRs I have are Dakki, Prometheus, Brahma, Michael, and Arty. Thinking about heavily helping my fire comp for the upcoming wind tower, but honestly just feel like it would be better to go water/wind and at least clear everything >_<.

Sorry that turned into a bigger rant than intended.