i think i'll propose this again.
in 1.6's wc3 mod, humans were damn near invis with a knife out in the right spot. use the current invis value or previous invis value for when the human has a knife out. the effect is reduced when any other weapon is deployed. i think this would work SO much better. you could still sit damn-near invis in a corner, but you have to time your shots well and tactically switch between knife and guns.