Depends.
With my build and NCS I need about 2 times as many hits on plate as on mail (nevermind the glances). But the higher damage the weapon is the less that is true. Str build with tripple heirloomed axe will maybe only 1.5 times as much damage to mail than to plate, that's where the offender is.
Especially since the number of hits you can take is always an integer. I.e. if someone hits me for 90% hp in mail he will still do 60% hp damage to someone in plate, 2 hits in both instances. But if you manage to kill him after the first hit, that is a huge benefit. I've been killed alone by random horse touch from 10% health left 5 times in the last two days, with just 10 more armor I'd have easily survived and the speed hit isn't really noticable.
Seriously, if you are looking at the people that pull out plate every once in a while, their K:D skyrockets but people will also pack higher damage weapons or go for gangs and headshots if they see a plater.
Urlurkur suggested to change soak and reductions values so that high damage weapons don't bypass armor so easily, or you could give everyone more hp so the difference is more pronounced.