This is such an old thread, but I'm going to post anyway because I was just looking at this archetype today because I'd like to play a good thematic poisoner for Serpent's Skull.
I think it would be more appropriate to revise it to allow more rogue talents that modify poison instead of only those that modify sneak attack. A lot of them are much better than the alchemist discoveries for poison (Signature Poison vs Malignant Poison for example). And while it's not written that way, I'm just going to assume that all of the combat style feats were intended to be replaced with rogue talents, and not just the one at 2nd level. Hopefully my GM agrees.