Health Link elites glitched? Give more NV than they should

So I was doing a run of Inferno Act 1, and the first elite pack I found had the Health Link affix. I killed all three of them simultaneously with Revenge, and I got 3 stacks of NV all at once from that single group. On my next run, I ran into an elite pack with Health Link. I killed one of them, then killed the other two simultaneously with Revenge. I then received 2 stacks of NV from that one group.

Is this supposed to happen? Does it have to do with how many you kill at once?