When Lee Sin Centered dies during combat, does his ability stop buffing other units mid-combat, potentially causing them to die from already-assigned damage?

Ruling: No, units buffed by Lee Sin will not die from combat damage even if Lee Sin dies during combat, because combat damage is assigned all at once, then units are checked for death, then all units heal before a second cleanup occurs.

Sequence:

• Combat damage is assigned to all units simultaneously
• In step 2b of combat cleanup, units with damage >= might die (Lee Sin dies here, but buffed units still have his bonus so they survive this check)
• In step 2c of combat cleanup, all units heal (damage is removed)
• A second cleanup occurs after Lee Sin's death, but the buffed units no longer have damage marked on them
• Result: The buffed units survive

Nuances:

• Outside of combat, if Lee Sin is killed by a spell like Singularity, buffed units CAN die in the subsequent cleanup because there is no healing step between the first cleanup (Lee Sin dies) and second cleanup (buffed units lose the bonus and die to marked damage)
• The defender must assign lethal damage to one unit before assigning damage to another unit
• Spells with "do this:" wording (like Falling Star) resolve their damage instances separately, while spells without it (like Singularity) deal all damage simultaneously