Really, the big problem Xara and Corban have had is bad dice rolling. You're living in the tail of the bell curve, and that sucks.
(it's why, in general, I dislike the way RPGs tend to use dice -- because it's clear designers didn't spend time actually thinking about the statistically unlikely, but actually possible, incomprehensibly long string of bad luck. If enough copies of the game are sold, *someone* will experience that, and it's worth designing a game, I think, so that worst experience is fun. It's also why, when I build D&D characters, I always optimize "to hit". I'd rather hit and do a little damage, than to miss most of the time and do big damage when I hit... because missing is sucky and not fun, but hitting, even for a little bit, makes progress).
What's kind of funny, is the enemies have been living in the same probability tail and so we've had a wonderful combat experience where almost NOTHING has happened for 3 turns. Them's the breaks of dice-driven combat resolution I'm afraid. You're best bet is to hedge your bets and use and gain Advantage.
Actually, there is something *I* can do and I think it's called for - Corban and Xara gain Inspiration (if they didn't already have it). You can spend that before your roll to gain Advantage (roll 2d20, take the better). You gain Inspiration for RPing well, and the two of you have been RPing DAMNED well, especially given that nothing has happened, you've kept a lot of the life in the particular exchange you're engaged in.