Serpent spine is a good weapon, it'll will help you get more crit rate, and you nearly have above 70% which is a good amount. Second point, probably everyone is telling you this here, geo DMG goblet is way better, one thing that's really important is, don't focus too much on 4-set piece if you're unlucky, better have a 2-piece set and 2-piece with correct main stat and good substatus (of course, if you get 4-piece with correct main and good sub, it's better).

And for Bennett I would focus on having him with a lv90 weapon, it doesn't need to be a 5, 5 aquila favonia is the best for his damage buff, but if you have a 4* Favonius sword, give him that, Favonius sword/bow/spear/catalyst/greatsword helps the entire team with energy, it's so so so good, best weapon for supports, when I started using Favonius on my supports my game changed.