Players can live their own choices. Tukufu does NOT volunteer his blood thank you very much. And as a psion he heals himself. Other PCs are welcome to make other choices...and maybe someday deal with the consequences.
NPCs are a somewhat different matter. Unless its on a relic or CP signed off by a judge (and/or I think it seems reasonable) I don't particularly feel bound by any given Sarishian's alleged collection. Though careful "account keeping" might help I'm going to make a ruling on what I think is reasonable and roll from there. If for example Arch Prelate Leona goes missing and a PC says AHA I met in module X and she gave me a drop a blood ... well, I've probably played, read and judged X. If she's not injured in the mod AND I don't see how or why you'd ever get a drop of blood from her...then I don't feel that as a judge I have to honor that claim even if some other judged signed off something like ... "yeah she volunteered a drop."
That said I generally don't care to nerf PC powers. Especially the ones that don't turn up much. So if it made sense I *might* try to throw a blood tracker a bone even if the module didn't really take that possibility into account. I would note that I've never seen a module "broken" as a result of this so I am not that worried...
Last thought. IMO important NPCs don't make themselves available to PCs "convenience." They use PCs when its convenient to them. If a PC asks for a drop of blood I'd politely decline but offer to hold a drop of the PCs blood instead.