More often than not, blood coagulates too quickly to use as an ink, and ruins nibs. Traditionally, when someone wanted to write with blood, their pens were quills -- literally feathers -- and were frequently sharpened. Quill feathers, even properly heat treated (as pens not treated were far too flimsy for most applications), wear down rather quickly. With more durable writing implements, such as metal nibbed dip pens, blood was mixed into the writing ink to incorporate it.
This was not just for magic, but also since blood has a deep connection, and using it was more symbolic of sincerity, oath, and personal connection. That is one origin of having a blood bond: one's blood was used to sign a contractual bond.
So in the case of touching the nib of a ball point pen into one's blood is still, in my opinion, valid in the intent of the ritual.