So what is the most poplar loadout for phantoms?

From what I remember and tested, Final Cut is a 1.6x skill damage bonus. From what I know about Cross Surge, it isn't a 80% total damage buff, it's a 1.8x damage range buff, used to be 2x damage range but after the nerf it changed of course. This is compiled up from all the Drks that tested this several times in the past. Arrow Blaster (nerfed) in all honesty is even weaker than Mille Aguilles and too slow to be a benefit alone unless you're using it for special cases like Gollux. Summon duration was also nerfed by the way or broken, since it doesn't last 30 secs anymore, its more like around 25. I can't tell you whether no CD Final Cut will win over Rapid Fire unfortunately since, they perform differently. It's sort of like trying to kill Chaos vellum with Arrow blaster alone vs using Rapid fire, there's different issues involving both cases.