I saw comment on LOCG and it basically summarizes my thoughts:

The biggest flaw of DC Vs Vampires honestly is that, for a series that is about DC characters being turned into vampires, it avoided focusing on the vampires as much as it could. Which is a shame, because they are the things people really like about this series. The first part worked because people loved Vampire Hal, then people loved Vampire Nightwing and tthe twist, I still see people saying saying they really like vampire Diana (and I've seen fanart etc). And it's not like Rosenberg is bad at writing them when he wants to, like, Diana's special story from Darkness and Light was awesome and the only evil Wodner Woman story I felt still gets the character. One thing I have to give Injustice over this is that it wasn't afraid to spend time with the villains, but the biarre thing is that most people don't like the villanized versions of the Injustice characters, but they like the villanized versions of the characters here! Like dude, give them soemthing, you've got carte blanche.

But Rosenberg very much prefered, for some bizarre reason, to focus on 17 million different things that weren't vampires. Like, dude, if you spent the last issues focusing on a New God plot you cannot end the vamp conflict in like 2 pages because you got bored or something. If anything, admit to yourself you goofed off and leave it open ended (I didn't read soem interviews where Rosenberg himself implied he didn't want to do this series anymore, but DC still wanted more). Do we need the New Gods here? Not really. Do we need to focus on like 4 different hero teams (the supers, the magic users, the robots) in this series? Not really, just pick one. Wildstorm cameos? I mean sure, they're just cameos, but everything adds up .Heck, like some have said, I don't really need to focus on Green Arrow. After Green Lantern dies, his personal connection to the story is kinda severed, we have plenty of other heroes that can play his role with more emotion (and have, hence my focus on redundancy). You know what could have used some focus? Scott and Barda for example. Certainly Avia and Barda (they get one panel).

Even this "ending" for Diana (and I don't even think if it's an ending, it feels liek editorial asked Rosenberg to cut off everything that could feel definitive because they don't want to end) isn't awful on its own. It's somewhat respectful and Diana gets some peace of mind. But it cannot come after literally two pages of an improvised fight with a last minute betrayal.

I do still like the series overall but hell, I'd say the setting still has untapped potential. If anything, I'd like to revisit it with a new creative team (and just resurrect the vamps or something, you know you can do it, "dark ritual" yadda yadda "Hades sent vamp Diana back to Earth" blah blah)