I keep getting drained by those Vampre Totems too quick when 3 are created. I can't move quick enough to destroy them and my potions take too long to regen health.

What is the suggested level for fighting the boss? Any strategies?

I suppose You play on Hard Mode if You have problems. Use Diamond Demonic Power along with Hunter Suit. It will greatly enhance Your survivability. You can also try using Foil with Charge skill to quickly move between syphons.

The vampire loses health fast with the rapier's bleed ability. The pylons can also be destroyed quickly before they can drain a significant amount of health.