upon further reading the errata changes this to:All strikes from a single Fight Action must be made with the same weapon, so a model armed with multiple different melee weapons must choose which weapon to make its attacks with in each Fight Action.
All strikes from a single Fight Action must be made with weapons of the same weapon type (one-handed, two handed etc). A model armed with multiple melee weapons of different types must choose which weapon type to make its attacks with in each Fight Action.
So as an example,the question asked by connor yesterday, yes Tainted Walks Looking can attack with her demonic blade and her bite in the same Fight action as the one handed weapon rule says
So for each strike she could make 1 demonic blade and 1 bite or 2 demonic blade attacks.One-Handed
A One-Handed weapon allows a model to Fight or Shoot with up to two of these weapons per Action.
Going to go re-read the rules about multiple shooting weapons now.