Just a question about weapons.

In the case where I have a few (3 of them, 4 after this event) 3* off-element SSR weapons, and a bunch of off-element 3* SR weapons, is it worth leveling a 3* Defender SR Weapon of the same element?

More specifically, if I don't have a dark grid, but I do have other element grids, should I go for dark defender weapons or not?

Also, for SR weapons that I probably won't get another copy of (gacha weps), is it fine to use them as skill level up fodder?