Does Adventurer ring instakill work vs aliens?

After 1000 attacks I will say that it does not.

Have you tried it wearing "NO" bing/visitor equips? When wearing none of those snipe shows up as a miss, but still kills, whereas when wearing a piece of the suit, it is forced into the set number that the rest of my attacks do, while still OKOing. Unlikely as it may be there could be a difference there.