Wizard, sorcerer and warlock are all synonyms - and could encompass a D&D bard, druid or even ranger - but the game gives them a precise meaning. I don't see Mystic being any different.
But psion was good, it comes from "soul", and I don't know why it has that strong of a sciencey flavor.
I particularly liked the sciencyness of the previous editions' psionics. It felt different. There is the natural world, and psionics where sort of themed to be a piece of the natural world. Like an animal in nature, there is also this thing called psionics.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.