> Or else all lightforge weapons would be doing like 2x or more damage to undead.
Why? They're either energy/light or silver/physical. Undead aren't vuln light. Some undead (skeletons) are vuln blunt, and many (but not all) are vuln silver. So silver/blunt on skeletons that are vuln_silver would apply two vulns.
> Silver, blunt, positive maces?
How could damage be both blunt and positive? They're two different damage types.
> an average 24 steel mace that is wrathing does the same damage as an average 24 silver mace that is wrathing.
Only if you're attacking something that's not vulnerable (or resistant) to silver.
> Similarly, a dark elf that is branded by the phoenix does not take multiple vuln multipliers from wrathing mithril swords/daggers.
If he got the wrath vuln from phoenix brand then, yes, he would suffer two vulns from a wrathing mithril weapon. Assuming he wasn't resist_holy from gear or preps. I'm not sure what the interaction would be between phoenix brand and resist_positive; I'm guessing it would work like racial vulns do, in which case the resist would override the vuln from phoenix brand.