I've got to agree with all of the other reviewers, Bloody Cross is far from horrible, but it's not worth going out of your way for. It just lacks that certain something needed to make it memorable. More like, it's as middle of the road as you can get.
The plot of the manga is actually pretty good. While yes, Tsukimiya and Hinata start off with a cursed mark that will kill them if they don't act fast, that problem is solved within the first few chapters. The real plot to this manga is everything that happens after that. Namely, to get rid of their brands, Tsukimiya and Hinata have to get hold of divine relics that, once collected, will turn the user into the next supreme being of the universe. An angel also hunting the relics is impressed by Tsukimiya and asks her to assist him in his quest to become god. He'll pay her to help him track down relics and keep the ones he's got safe. And that's the plot for the rest of the manga: tracking down relics, tricking other god candidates into giving up their own relics, making alliances to get more relics, breaking those alliances, etc. The double-crossing and the intrigue are probably the strongest points of this manga.
On the flip side: The art for this manga is serviceable. There are no awkward angles or proportions, the action shots look the way they're supposed to, all of which is very good, yet the art comes across as somewhat bland. The artist incorporates few details, placing the characters on big white spaces most of the time instead of actual backgrounds, and the characters are drawn in a generic way. In point of fact, so generic that even after 6+ volumes of manga, I still have a hard time distinguishing between them...
The characters themselves are another issue. Unfortunately, this is one of those mangas that likes to continually spam readers with new characters. Each new villain arrives with an entourage of henchmen (who once again, tend to resemble on another), so it becomes quite a chore keeping them all straight. In some ways, it's logical to have so many characters; after all, we're talking about divine relics that grant the user the power to become a deity, of course there would be multiple factions trying to get hold of these things. However, with so many characters, there ends up being very few that I care about. In short, the character development is seriously lacking.
The manga tells us very little about any of the characters, including (unfortunately) our main character, Tsukimiya. For example, not once has the manga mentioned her parents, yet she's supposed to be a "half-blood." But how did an angel and a vampire end up having a baby? What happened to them? Are they currently alive or dead? How long have Tsukimiya and Hinata known each other? What does Tsukimiya do for a living when she's not hunting relics? These are pretty basic questions, but the manga is more interested in getting to the next plot twist than answering questions about its characters.
So I'm not going to tell you to run out and get this manga, but I'm not going to tell you to avoid it either. There nothing in it to really hate (and nothing in it to really love), so yeah, a really middle of the road manga.