>>3534
dust is already better than sentries for killing / ganking heroes that use invis to escape.
it 1) slows 2) isn't area limited 3) costs less than sentries
60 second cooldown is just to make it so you can't just dust the same hero twice in the same gank unless you have multiple heroes carrying dust, though I'll admit it could be lowered to ~40 seconds and not be too strong