Harris and Jackson are both pretty good. But that's their ceiling.
By the end of 2016 J. Jackson had passed them both.
Garvin's got the fast-twitch gene that Harris/Djax seem to lack.
I don't think it will happen immediately because Harris and Djack are good players with a lot of experience but Garvin being here for the spring is a problem for them.
Though your word is irrefutable I think DJack has room to grow. He was raw, added a ton of weight, then got hurt. I think we know what we got in Harris but DJack is still growing into his role. May not realize his potential till the NfL