Not sure how much of a tip this is (more common sense), but one thing I've found helpful is putting my 4 star units that buff the solar blast or have stage bonuses (as opposed to the combat buff units) into my weaker teams or the ones with less aoe. It helps with splitting up power and blast does really good damage to a 2/3 unit group.
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EDIT:

This thread actually helped me a lot with 10-5 (since it was just as annoying as OP said) so I figured I'd add what I used on it too.

->Open Spoiler<-

Following the advice, I made slow teams with my fast team running at the bottom and my team 4 being on the top


I was having a lot of trouble until I removed girls from some of the teams due to them killing the boss too early. Low 40k power felt the safest for the top team, but the other 3 teams that had a chance to fight the bottom boss + pest node had to be a little stronger. I also saved solar blast for all of the fights except for the bottom boss and the pest node after it to make my teams take as much damage as possible.

Helper had ~380ish speed, so I lucked out a bit there