The stats gained from the shoulder pad dont count into wearing other equip. My shadower has 149 dex without mw20 or shoulder. after equipping the shoulder I am still unable to use my weapon. As you can see in the photo below all the stats on the kanzir marked white which means I should be able to use it.
Thank you for reporting. I presume you were still able to unequip and equip the weapon? But the client turns the slot red once equipped and doesn't show the weapon on the character itself? I've spent a bit of time looking into this, but it seems like it is going to be a client edit, so will need a little bit more investigating.