User blog comment:Willbachbakal/(Champion Rework) Cassiopeia, the Serpent's Embrace/@comment-4888212-20150728230657/@comment-1330314-20150729014350

The issue with building attack speed is that it would only increase the initial ramp-up without improving Cass's damage after that. Again, stacking poison with autoattacks alone would require at least 7 seconds of constant fighting as a baseline, during which Cass would deal far less damage than anyone else and put herself at far more risk too. There is no issue here with her applying her poison on her autoattacks.