I think part of the reason that the eFG has dropped for some of those guys is that people like Gipson and Diaz now have the freedom to shoot 18 footers whereas last year that would have never happened. Martavious is taking guarded jumpers from 19 feet with 22 left on the shot clock. They aren't worse shooters than they were, they are just taking different (harder) shots than they used to. I think with this group, you will see people's eFG drop significantly from last year.
Diaz took quite a few 15-18 footers last year. I think you are suffering from Franknesia. Gibson has taken a handful of those shots this year and hit a couple of them, not like he is jacking up shots like KG from the elbow or anything. I think the reason we are seeing our eFG go down so much from last year is our lack of intensity on offense. Last year every player on our offense was moving at all times. That pinwheel really made the other team chase us for the entire shot clock. Eventually it would mentally/physically wear them down and they would start to make mistakes that would lead to open shots for our guys. We are very lethargic on offense this year. Most of our screens are totally halfassed (quarterassed in Diaz's case) and the off guard is just standing like a statue behind the arc the majority of the time. We seem super lazy when it comes to doing the things that REALLY create open shots ie hard picks, hard cuts, crisp passes. I think this offense would be fine if we had players who were more capable of creating space for their shot, bigs who were better passers with better hands, and we had a JYC mentality when it came to doing the little things. We don't have those things though, so maybe it's time to tweak it a little bit.