the Heretics were poorly worked, if they had added more age to them like for example vampires created a while after the first generation of elders like Sage and Troy, or Aya...The elders vampires : Aurora, Tristan and Lucien, it would be very interesting they would be formidable threats with 1000 years or 900, aside from the fact that they broke the whole Heretics story to link them to Stefan and Lily, shortened their age, Nora and Mary Louise's initial blurbs said that they were around 150 years old since they were together as a couple, so when the series started they shortened to transformed in 1864/1865, in addition to the fact that they weakened them in the script for Stefan and Damon to beat them more easily, in the synopses it said that Valerie, Nora and Mary-Louise were very powerful and together they would do terrible things for revenge, they three needed to be together to perform certain spells that common witches did alone.

Heretics sound good on paper but in practice they had a fatal flaw in there existence. Siphoning from themselves shouldn't be desiccating them as that has to do with Blood flow. It should be killing them, stripping themselves of the magic that created them. There siphoning should be acting more similar to the anti magical barrier.

In truth they wouldn't be that powerful unless they had an immense source of magic to siphon and Vamperism isn't it. The stronger they become as witches the weaker they become as vampires and the weaker their bodies become. Thus they would be more susceptible to over exhaustion.

heretics would be formidable if they were well crafted Valerie was the first even though she wasn't a original Vampire with Klaus or Hope,

she should have an exception to the other Heretics at least a superior immortality, besides the fact that witches increase their powers with practice Dahlia was weak and remained powerful after centuries , heretics don't have this advantage if they shape their powers like a natural witch, they can self-destruct, and that's wrong, if they function like normal witches with a source of their own, this should amplify their magic and strengthen their vampirism. that amplifying this magic by practicing they would get stronger would be a powerful loophole as they wouldn't need to age to get to that point Valerie would be more dangerous than a 100/200 year old vampire, and if they reach the peak of their power (amplifying this magic not absorbing everything!) they would be similar to vampires like Aya in that vampirism magic would increase with centuries of practice while in the living world, and if they got to Aurora's age with that practice they would be very dangerous.