Light and dark have the advantage against all other elements and even so with each other. They are one-sided towards the player's advantage, meaning your light and dark teams deal more damage to dark and light enemies while receiving less damage from them. That's why many prioritize a dark or light team as they can handle all content without needing a back up.
As for the weapon, level up 3 of your dark SR raid guns and replace them with your SR HP weapons and break them as you get more and eventually replace your gatcha weapons that probably won't be getting max breaked any soon. The only reason you should use SR HP weapons is because you need an equip for your soul or if you literally have nothing else. They're a waste to use and yours aren't even that high or that far off from a no break SR weapon's first lvl cap, so using the 3 of the guns at no break would be a better option. If your SR HP weapons were maxed out for some reason, then it'd be different.
If you had put more effort into 1 team while slowly working on the rest, you probably would have been able to to do Ragnarok, which is a rather important thing you want to be clearing as cores are especially needed for things in the future and you can only get so many per event.