Interesting question Ferfey.
I'd simulate it but sadly Kahorie's sim is not so good when you exclude Epidemic (details). I'd have to use a rotation file instead, which would mean I don't have a like-for-like comparison anymore.
With shorter disease duration, you would have the problem though, of blood plague dropping off in the 2nd half of your standard rotation, and that would mean obliterate would do less damage then. I wonder too how it'd pan out but my gut-feeling is it'd be a net loss.