I'll try to get some thoughts together, too, but noting right now that once Sera moves, it looks like Jan can autohit and autokill Bowman C. This will free Alisa up if she needs to back up Athros. Don't know if Jan will do so though, since NPC.
On the left, Karima and Marcianus go down in 2 or 3 hits. If Taukek goes to E-11 (edit: ah, assuming the skirmisher actually didn't dodge something and survive, in which case we're in more trouble) and dismounts for hilly terrain bonuses, he can take some heat off them, but it's still a very real possibility that two people out of three go down. I can provide calculations if need be - Taukek at least definitely requires three of the enemies to burn their attacks to down him, which means that if he's focused, we have a greater possibility of two out of three people staying up instead of one out of three. Don't know if it's worth it. We'll most likely have to retreat next turn, although our counterattacks may whittle the enemy down - so maybe the situation will change.
Athros is probably fine. Scouts only do 8-3-2=3 damage to him while he's on the hill. Adepts do 10-1-2=7. Bowman can't reach yet. Bowman can reach, does 5 damage. If both Scouts and the Adept hit him, he takes 13 damage - not enough to down him. If all of them hit him, though, (unlikely given his high evasion + hill, but never say never) he does get downed. If Diane moves to the right as far as she can, Ghamina can dance her and Diane can move somewhere where she can reach Athros next turn, meaning that he can be kept up almost indefinitely if need be, protecting our flank.
Don't know what to do with Alisa. If Jan doesn't go to attack Bowman C, she should probably secure the kill. Otherwise she can support Athros for extra insurance or go left to form a more solid front.
Sera could probably move forward and vuln herself. No point in moving backwards - the left needs more help than Athros, unless the enemies begin shifting his direction.
I'm wary of retreating to or staying on the narrow path in general. We're still going to get swarmed (and the enemy mages and bowmen will rain down hell on us) with a ton of shuffling required to get access to a healer, and have to burn our vulns anyway. The majority of our concerns are ranged, with only the Shield-Bearers being serious threats in the melee department. At least in the general vicinity of the hills, we have a better chance of spreading out and evading enemy attacks.
yeah, i dunno.
Alternative 2, depending on what Taukek wants to do: If Taukek moves back, grabs Diane, moves to E-15 and hovers over the mountains, Sera can move up to E-14, grab Diane, and drop her on D-14. Although Sera won't be healed this turn then, she's protected from ranged enemies by Marcianus at E-12, and Diane will be able to reach Karima and Marcianus next turn to heal. Downside is that Athros will have to vuln himself if hit in the next few turns and hold out best he can. It also leaves Ghamina with only Athros and Alisa to dance, neither of whom have any good reason to take two turns - unless maybe Alisa moves forward and vulns Sera.