Well two of them:

So If I go full Batman-saga, and I have 4 drop Batman, Twilight Vigilante, who reads:
Concealed-optional. whenever batman stuns a defender, its controller loses additional endurance equal to its cost.

Since his effect triggers when batman stuns a defender, does it stack in a team attack with multiple bat mans ?

EXAMPLE: If I team attack with 3 drop batman (lets say problem solver), and 4 drop batman (twilight vigilante) into a 4 drop, how much does my opponent take? Is it 8 or 12 or 16? (4 (4 drops initial cost) + 4 (Batman, twilight effect triggering) + 4 (batman, twilight vigilante effect triggering) )

He takes 8. Anytime a card says it's name it means, "This Card."

So what Batman means is, "Whenever [This Card] stuns a defender, its controller loses additional endurance equal to its cost." To do what you're thinking it would have to say "whenever a character named Batman stuns a defender."

-Mike

If your going golden use the 5 drop that does the same thing. Team attack with the four and five and take triple stun!

Bwa ha ah ha.

Recently posted a non-Clone Saga GA deck on this exact topic in the deck garage.

Adamlee - took it one step further. Tossed in Darkseid's Elite and Teen Titan for a odd initiative turn 5 kill doing 5XStun endurance loss with both Batman, Caped Crusader and Batman, Twilight Vigilante protected from being stunned by Dynamic Duo and equipped with Beta Clubs.

Linky: http://www.vsrealms.com/forum/showthread.php?t=62385