How can a weapon be silver, blunt and positive? It's not even possible. The weapon damage noun determines what type of attack it is. Just because maces are in theory blunt weapon, doesn't mean they are all blunt weapons. You have have a silver and divine mace that won't exploit a blunt vulnerability.
And yes, vulnerabilities do stack. The skeletons on Calandaryl are vulnerable to divine and silver. If you have a divine + silver weapon, you'll be doing quite a lot of damage. It was easy getting unspeaks with a silver maran staff, because I was exploiting blunt and silver.
The problem with your theory is that you think the silver maran weapons have a divine attack. They don't. They have physical attacks. Only the energy weapons have the searing light attack, which isn't even a wrath attack.
Also, phoenix brand doesn't necessarily make a person vulnerable to wrath. It can make them vulnerable to fire and light.
Yet another reason why there is so much misinformation spread around these forums. People talking about things they don't actually understand.