It took four tries, but managed it. Took a team of Ra, Tempest, Nightmist, and Argent Adept. The environement was Pike Industrial Complex.
Tempest and Ra did a good job in the early game scrubbing out the thugs and underbosses. Nightmist got her amulet out one round too late to stop the Hired Gun, though, and that hurt (7 damage each).
By the time the five underbosses were down, everyone was down to single digit hit points, and it looked like a lost game. When neither of the main damage dealers can survive doing their damage, it starts to look bleak.
Then, Nightmist used Mistbound to stop the Chairman from drawing cards, and Argent Adept and Tempest did a good job of keeping it cycled (Reclaim from the Deep and Vernal Sonata). That stopped most of Chairman's offensive output. Sadly, Tempest never drew his healing card, which would have helped the end game immensely. Ra and Tempest ended up spending too many turns idle, because they couldn't survive the damage coming back to them. Ra started playing redundant Staff of Ra cards just to get the 3 hp back.
Basically, the end game consisted of Nightmist and AA tying up Chairman and Operative, and arranging turns where either Ra or Tempest could attack with good economy of damage.
It was a fun game, and it felt one Vat explosion away from defeat.
Who was Ra damaging when he threw out his old Staffs?