So, I seem to be having something similar also, relating to flagellants. For the *second* turn in a row I just had a thug defeated by the same group of unblessed flagellants. Not quite the same order of magnitude as the fire king, but still extremely unlikely and relating to flagellants so it made me think of this thread.
King of the Deep 24/25 protection, awe-0, ethereal, lucky (fatigue 44). I'd expect flagellants dealing 11+3 damage to only have about a 3% chance to deal damage to me if they can hit my head. Ignoring my (considerable) defense the luck + etherealness should reduce the chance of dealing damage by roughly another order of magnitude...so about 0.3% chance of dealing damage if they overcome my defense. Turn one of engaging the flagellants a little red 4, 6, then 14 float up from my guy.

That 14 damage alone has a chance of 0.0001% of happening, the chance of getting hit 3 times (15 x 2 attacks occurred) boggles the mind...never mind that something similar (don't have the turn to recite specifics, that dude's dead) happened with the same flagellants the previous turn.
Trying to strike agains Awe 1 (mor 18)
10200 striking with weapon Flail. att33 def21
hitloc Flagellant strikes King of the Deep wl3 diff0 -> 3
hitunit 10200 2440 dmg3 spec2097159 ba3
10200 striking with weapon Flail. att25 def19
hitloc Flagellant strikes King of the Deep wl3 diff0 -> 3
hitunit 10200 2440 dmg3 spec2097159 ba3
damage 4 on King of the Deep, spec0x200007 ba3
Ethereal failed
Trying to strike agains Awe 1 (mor 18)
10174 striking with weapon Flail. att19 def16
hitloc Flagellant strikes King of the Deep wl3 diff0 -> 2
hitunit 10174 2440 dmg3 spec2097159 ba2
10174 striking with weapon Flail. att13 def8
hitloc Flagellant strikes King of the Deep wl3 diff0 -> 2
hitunit 10174 2440 dmg3 spec2097159 ba2
damage 6 on King of the Deep, spec0x200007 ba2
Ethereal failed
Trying to strike agains Awe 1 (mor 18)
10201 striking with weapon Flail. att15 def6
hitloc Flagellant strikes King of the Deep wl3 diff0 -> 2
hitunit 10201 2440 dmg3 spec2097159 ba2
10201 striking with weapon Flail. att19 def7
hitloc Flagellant strikes King of the Deep wl3 diff0 -> 1
hitunit 10201 2440 dmg3 spec2097159 ba1
damage 14 on King of the Deep, spec0x200007 ba1
Ethereal failed