Phisycal damage yes. Healing absorb debuff no. Here is screenshot from PTR 5.4.x with necrotic strike absorb: http://s003.radikal.ru/i201/1403/96/1f16a407503d.jpg
My stats is: 30768 attack power, 42.72% pvp power. Target have 80% resilience.
Formula for absorb from necrotic strike: Attack power * 2.25 * pvp power * (1 - Resilience) = 30768 * 2.25 * 1.4272 * 0.2 = 19760 (Same as screenshot. Have a small difference, but im sure thats because of rounding or something like this).
As you can see, armor is not calculated here.