: Well, several things point against this.
: 1) Both Balor's appearance at the beginning of the Great
: War and his impending death (Pools of Iron or River of
: Blood opening narration) were heralded by the comet
: which had indicated the rise and fall of the previous
: levelers.
Actually, it was only his death; and his death, and more strangely the comet's appearance and Tharsis' eruption, were fifty years late! The cycle began in 2431; Balor should have appeared, killed Alric and wiped out the Light, died or vanishes, and left a Dark Age to rule for a thousand years. Instead he appeared, wipes out MOST of the light, and then 50 years later the comet and Tharsis show up and he gets his ASS KICKED by that slack-bastard Alric.
: 2) Balor appeared at the right time to be the leveler
Almost. See above.
: 4) The cycle would be even more messed up if one of the
: other fallen lords were the leveler.
Indeed. Or, as occurred to me as I wrote the above, if the Emperor who Balor killed had been the Great Hero!