A lot of the concerns about diseaseless Blood play make a few assumptions:
-- Someone else is providing the tanking debuffs (presumably without a major dps hit).
-- You can AE tank fine without diseases.
-- You won't use Outbreak.
-- Your threat generation will be fine without diseases (or at least the trade off will be worth it).
Those are all risks, but I don't think there is enough evidence yet how they will all play out at 85. We're still a long way from the diseaseless dps rotations of yore. If they do all turn out to be true, to the extent that skipping diseases becomes the typical way that tanking DKs play, then we're likely to do something. Something could include giving Heart Strike or Death Strike slightly more dependent on diseases.
Recall however that we changed things to their current state because too much ramp up time for a tank can be really painful. You don't want to have to get all your diseases up before you start generating decent threat, and when DKs are balanced around so much self-healing, you can't be expected to always have time to get diseases up when you really need that Death Strike heal. Perhaps there is room to come down a little. We'll see how things play out.