Short answer: I don't think his absence is hurting the story or the character dynamics all that much.Any thoughts on the absence of Cyborg? Like, is it working well without him, does he seem to be missing, or not?
Right now there's sort of a weird surrogate family dynamic developing with Dick & Kori as the big brother & sister/parental stand-ins and Rachel as the little sister with Garth as her friend/prospective boyfriend. There's no real status quo on the show so that's by no means how things will remain, but for now all adding Victor would do is to either give Garth another friend or add a second big brother figure.
This is just my opinion, but even in the comics (at least the original 'New Teen Titans' run) I always got the vibe that Victor felt just a little bit superfluous. Even in the cartoon I think he was mostly there as someone for Beast Boy to bounce off of. Honestly, he's a better fit for Justice League IMO.