I don't think offensive sets have much merit on this mon outside of gimmick. It isn't that strong, and not fast or bulky enough to easily set up on much.
Personally I've found it to be pretty underwhelming overall, though I haven't yet used it on one of my own teams. The only set ive seen have success is SpDef pivot, which acts as a nice check for Rain teams, and alright utility as a pivot.
Maybe if some monsters in the meta get banned, Decidueye can gain more traction, but I really don't think its combination of traits set it up for much success in OU. The defensive typing is not that good, and it's pretty average in most stats with no real outstanding traits except a nice movepool (which I also wouldn't call outstanding). As an example from last gen OU, Infernape is a mon with an excellent movepool and many touted it as versatile. And yet out of all these things it could do, none were that good. The problem was its lackluster stats (outside of its nice speed) by OU standards and it was relegated to a niche defensive role mostly.
Decidueye may end up being OU simply based on usage, much like Sylveon and Conkeldurr were for a while, but I'm failing to see a lot of viability to be honest. This isn't to say there is no point in trying it out and discovering new sets -- the meta is young -- but I'd be surprised if this didn't end up being a niche pick with usage defined more by fan favoritism than viability.