Through all the previews and speculation, I hadn't really considered the card much, just another Threaten type effect in a long line of vaguely similar spells.
The card is a sorcery, which might have had something to do with my obliviousness. Released in a block right after Act of Aggression, it's hard to go back to looking at sorcery-speed effects as worthy of my attention.
But we definitely should. Or at least I definitely should.
Because Traitorous Blood gives the target creature evasion in the form of trample. Better than flying, in fact, because trample gets around any of the OTHER creatures who might have flying.
There are creatures who just sit around and get fatter in EDH. Kresh is one guy I can think of right off the top of my head. Vulturous Zombie is another. But there's really a whole class of them.
The reason for their slothful ways usually involve the large quantity of potential chump blockers hanging out around the field. Small flyers, utility creatures and more are always ready to dive in front of a potentially killing maneuver.
But now the damage gets through in most cases. And heaven help you if you have a copy of Nicol Bolas out.
Is it better than instant speed? Might be worth considering.