So..consider this a limited sample size but we spent an hour trying to hunt Sinuous Adders and Sable to get egg drop but no joy.
The next day i camped them by myself and while dual weilding a sword and a mace, i was seeing "crushing" damage and thought, well, thats not good for eggs. So I unequiped the mace and just used slashing damage (with procs). Egg dropped off Sinuous.
The next day I hunted them with my group, who attempted it before i joined them and they couldn't get it to drop. I joined and told them my slashing idea and we went 4 for 4 on Sinuous Adders to drop the egg. Mage and Shaman pets were used. The bard changed her mace for a rapier and dual weilded a sword. So it seems blunt damage is the main thing to avoid when hunting eggs.
Hope the rambling makes sense and good hunting!