With Kirabi essentially bloodlusted, and knowing that Gyuki is a giant target, he will likely use the V2 shroud. With that, his speed should be enough to dodge Susano'o arrows and quite frankly, dodge most of Sasuke's attacks. Kirabi also now knows the signs of Amaterasu so probably can avoid that even if he doesn't stay constantly on the movie. Kirabi is stronger than Ei, and with the V2 power, he probably is loads stronger (even with probably more than half his attack power absorbed, he blew off Kisame's chest; the same Kisame who survived Hirudora).
Battering down the defenses of Susano'o won't be an easy job, but neither can Sasuke sustain that jutsu for long. Odds are, Kirabi just outlasts Sasuke.