Necromancers were failed by-products in the form of living beings that couldn't properly utilise the magic around them.
That was the general consensus amongst the species living throughout the galaxy. They weren't off that mark either, as most of the necromancers only bothered to learn curse spells and, at most, raise a bunch of undead to support them.
However, most curses they used were easily countered with the help of basic healing abilities. It was rare to find a necromancer or a dark mage, as some called them, who could cause severe and lasting damage to anyone.
The combination of advanced technology and the easy availability of healers almost made necromancers useless. That was one of the primary reasons why Nico had his guard down, despite seeing how strong Ashton was just a day ago.