After Landing a successful heavy melee on an enemy hero, you have a window just less than a second to perform a powerful followup heavy melee that takes a little longer to charge but gives a powerful negative debuff to the enemy, maybe curse for 2-3 seconds?
It would be a risk-reward item since...
Only seems to happen if splitshot is bought before armor piercing rounds
Also landing multiple splitshot multishots on a single target while you have toxic bullets or silencer builds up the bleeds and silences at an equivalent rate. This may be intentional but infernus and haze don't build up...
Its probably due to the Boundless Spirit passive change as a side effect. If mirage was able to heal 100 health every second for free it would be broken, so they most likely completely overhauled the cd's and imbues on it
Holliday ult seems to not be affected by Debuff resistance at the moment. I know there were changes so that Debuff remover couldnt be used on ultimate abilities, but the actual debuff resist player-stat doesn't seem to do anything to Lasso. Apologies if this is supposed to be intended