As stated above, one way is to conserve the Fairy Dragons until the end and they will do a fair job of killing the servants.
Another way to take them out is to use your Sampire with an AI weapon, like a Bladed Staff, and go Enemy of One to them, and Honor as you can. With practice you can take out 3 or 4 at a time on you, but be careful not to get a Fairy Dragon on you too, as they do area spells and will re target you.
To take out 3 or 4 of the Servants at once, Use momentum strike and evade. when only 1 or 2 are standing, use AI and LS to finish them, as needed.