You're over reliant on stats and rarity. Don't get me wrong, the stats of the weapon are important, but mainly AFTER skill level. You desperately need higher skill level on your weapons if you want to hit harder. In your grid, I would mlb the lance and use 3 sr assaults (or better if you have them) and focus on their skill levels. Even basic sr assaults with lv10 skill is as good as your ssr assaults with lv4 skill (difference of the skill is 3% x2 per skill level). MLB what you can.

As for Eidolon, this is a bit more complicated. Depending on where you are (base atk wise), the 4% from an additional dark eidolon is worth differently. This also depends heavily on if you have a lot of anubis friends (because then it becomes 8% elemental atk increase). As a general rule though, it's best to try to fill your grid with dark eidolons unless there's a very good reason as typically the bonus is worth more than the 500-1k atk you'd lose (a good reason being: using a kaiser of an off element as a damage reduction mechanic, or a similarly vital skill for your team)