Just hit 54, fooling around on a dummy, I made this:

(prepare Abandon with Infur + Veng extend before pull) > HS(Brutal) > Maim(IR) > Eye(Xpot) > Fract > HS(late Berserk) > Fell(Infur) > Fell(Raw) > Maim > Eye(Brutal) > Heavy > Maim > Eye > Fell > Fract(pac)

I didn't math it out, just based on logical guessing/dummy practice, but with this, Eye is kept up the whole time, Fract is overwritten at 5s left with Berserk up, and 2/3 Fell Cleaves are buffed by both Berserk and IR. Any other ideas/math oversights I missed?