In the current release, I can't seem to fill the dark tank from the blood extractor. Right-clicking on any other block drops a block of blood as usual.

Thanks for reporting.
Which MC version are you using?

Further investigation (having made an infuser) indicates that the extractor can't feed blood to the infuser either, suggesting that the problem is with the extractor.

Forge 1901 (1.9) And for the record, "current" Evilcraft is 0.9.10.