As a infiltration\assault player I often find myself in pretty complex situations like 2 bullets in SMG, empty clip in a pistol and all i have is a melee. Currently melee has 2 problems: hard to understand when it should actually hits, because animation takes some time, second: you still need pinpoint accuracy to hit anything.
2 solutions: make melee proc in a wider timeframe and let it hit with a cone of at least 10-15 degrees. It can even hit secondary target if it's within the arc for smaller damage.
Otherwise it is quite useless, even more useless than pistols. It's kind of funny how description for double katar says its super effective in melee, when it's mostly impossible to hit anything with it, rather than standing afk targets.