Actually, that's completely wrong. I've done some extensive testing to find out how the two mechanics interact, and the results are... strange.
DT0, AR0.
100 = 100
DT10, AR50.
20 < Min
40 < 5
60 < 13
80 < 20
100 < 27
DT0, AR50.
20 < 7.5
40 < 15
60 < 23
80 < 30
100 < 37
DT0, AR25.
20 < 14
DT0, AR12.5
20 < 17
DT0, AR40
20 < 10
100 < 50
DT10, AR40
60 < 20
100 < 40
DT0, AR40
20 < 10
100 < 50
DT0, AR10
100 < 88
DT0, AR80
100 < 15 The first number is the damage the weapon should have dealt, before DT and AR are applied, the second number is the damage it ACTUALLY did. It's clear that AR is applied BEFORE DT. Moreover, an AR of 40 with a DT of 0 reduces damage by 50%, which is what SHOULD happen from an AR of 50. It's not a set percentage reduction; I don't know how it works.