For sillypuddy, all % Stamina increases are applied multiplicatively, to your current total stamina. That means that once a buff increases your stamina, the % buffs apply.
Essentially, you could just say that every 1 stamina from buffs and gear actually equals 1.XX stamina for you.
Madoxx. I'm a bit torn. It works fine, and the healing is very helpful for the healers counterbalancing healing up the huge health pool. Generally, I'm not happy with doing things as usual because I have other options. The smaller my health pool (to a point of course) the easier I am to keep alive, but as Blood I hurt my self-healing which is a part of my functional survival. I've been using an alternate gear setup that trades a fair amount of health and picks up a generous amount of avoidance and a bit more armor. I've also been using my Unholy spec a fair amount as it allows for more pure mitigation and some nice anti-magic tools.
If you're a traditional Blood tank, I think you may find Anub may test your healers and dps a bit more, though maybe not quite enough to really notice unless you're really walking the edge of success.