Orks vs. Vampires
The Vampires were wholly different enemies compared to the gnolls that the orks of this mini-horde fought previously. While the gnolls depended purely on their instincts and pack tactics, not to mention that they had poor combat skills and extremely low firepower, it was a different situation with the Blood Races.
Species that were categorized as the Blood Races, namely Dhampirs, Vampires, Kindreds and not to mention the pinnacle of their species, the Pale Blood were masters of Physical and Magical Combat. Even the lowliest Dhampir which were the hybrids of Vampires and Humans could compete in terms of physique against the weakest of ork boyz, not talking about the Vampires which were basically as strong as standard Ork Boy footsoldiers.