This was a great flashback imo. The fight could have been longer, yes, but the flashback has already been going on for quite some time. Also Roger, Garp, Xebec have rather generic fighting styles, and we basically know what they're capable of already. If Garp and Roger would have used some kind of tactic to win you'd all be downplaying their victory and strength even harder.
Xebec is definitely the man though. Great character. Also just amazing reveals all throughout this flashback. Hopefully we'll get some answers on how to deal with Domi Reversi when we get back to Elbaf.