Old thread, but since it’s still the highest relevant google result, I’m posting here.
Basilisk venom DOES proc the 10% damage on superior sigil of impact (tested 11/27/2014). Not sure if it was always like this or not (probably not when the venom was still uncounterable), and this may change in the future, but the numbers were solid. Can combine with sigil of force for a total of 1.15 (115%) damage.
Also, I don’t actually read the forums, just search things every now and then, so I’m not likely to see any replies, but if you don’t believe me, test it yourself! XD