Various is the correct author for any book with multiple unknown authors, and is acceptable for books with multiple known authors, especially if not all are known or the list is very long (over 50).
If an editor is known, however, Various is not necessary. List the name of the editor as the primary author (with role "editor"). Contributing authors' names follow it.
Note: WorldCat is an excellent resource for finding author information and contents of anthologies.
(Zero spoiler review) You know those 'you need to be this tall signs they have at the front of theme park rides? Well, DC most have had a 'you must be this bad of a writer' signs out the front of their offices during this run of Batman, and the bar must have been set pretty darn low, because god help me, this is woeful. The lead in issues are, at best, average. And it somehow gets even worse when the event kicks off. If you're someone who likes endless, pointless punching with little or no set up / characterisation / story / competence, then look no further. Otherwise, best to give this a wide berth. I got as far in as I could and then gave up. 2/5
I read this in the form of Book One and Book Two, and I really enjoyed them. I scored each with 4 stars, but together I score the entire series 5 stars!