the reason draconis is outperforming your other champions is entirely because of his gear. in much the same way that the difference between 5* and 6* champions is huge, just going from level 8 to level 12 gear makes an enormous difference in performance and the jump from 12 to 16 even more so. if you were to take his gear and move it to someone like dreng or deliana, you'd get much more value out of it.
athel and tallia have a few pros and cons (athel has better multipliers and is easier to book, tallia has higher base stats and slightly more utility) but honestly neither one is worth ranking up at this point. ronda is a much better magic dps than either of them. the only downside she has is that she's not as good a campaign farmer, especially early on when its hard to get her booked. you have skullcrown however, and she's one of the best campaign champions in the game so that won't be an issue for you.
kyoku meanwhile is one of the best champs in the game period. you are correct that her damage is mediocre, but she's not there to deal damage. her job is to keep the rest of your team alive and she is frankly amazing at it.
and yes, you absolutely should use those chickens.
Hmm......I suppose Lugan the Steadfast could use some of them chickens....