Getting rid of the three Vampire Clans was quite easy. For most Vampire Clans it was already surprising if there were more than 100 Vampire subordinates for each noble Vampire.
In most Vampire Clans one could find roughly five noble Vampires on average. Sometimes there were many more, such as in the battle where 6000 Vampires had been present but this was basically an anomaly that was not supposed to happen.
After all, each Vampire subordinate would have to receive a fragment of a noble Vampire's Blood Essence.
100 Blood Essences could be separated from a noble Vampire without influencing his powers negatively, but that was usually the limit.
In a large-scale battle against the Vampires, the noble Vampires had been unique. There had only been 10 noble Vampires of the same family, but they could regenerate their Blood Essence and thus create more Vampire subordinates.
That was also the reason why the fights against the first three Vampire Clans ended so quickly.