Can someone confirm if the same aura stacks with both weapon (dual lw for example)?

You want x2 of the same aura to stack?? I know you can stack multiple different auras but not sure about double stacking a single aura. I'd personally assume no you can't.

ofc you can, just like 2x dream or 2x dragon/hoj

That's true but only works on paladin, but your right dream helm aura and dream shield auras do stack.

Yes, you can stack 2x Last Wish on A5 Merc for level 34 might

no it works on other chars as well. auras from items on the same character always stack, but they dont stack with native auras on that character