Being born with, fated, cursed, unwillingly granted or trained in their powers makes MUCH more sense than getting them from "pacts".
Why/how give this kind of power from some form of "usurption"?
I mean in general, special cases are fine.
For example, "Ghost Rider" type ("Serve me or else!"); being born with it (thus it's innate); given it by vengeful spirits (whether you like it or not); a peculiar condition caused by the fury of elementals/titans (you unwittingly tap into this power, over time learning how to focus it)..and so forth.
Havign a core class who specifically, (and lot players will go this route), make pacts with fiends is NOT gonna endear D&D to folk (which includes a broader audience than the zealots). While the 80's silliness is mostly gone (and thankfully we got Devils/demons back), this is just pushing it a tad far, IMHO.
The moral choices should be broader, while keeping it "dangerous".
Yeah, we'll need ot see how the designers explain it
Disruptive players:
you all are lucky, sigh, I'm scarred for DM-life by a munchkin (sorry for using the word, but he was

), who managed to wipe or near wipe the party 3 times by his crap (once, I'm sure, deliberately), constantly grand standing, rules lawyering and bogging the game down, breaking rules/common sense to make the most apalling min/maxed characters, and several times nearly being assaulted by infuriated players, before we got rid of him...as much as some wanted to bury him under concrete as a new gaming table or garage, he was set free to haunt other poor souls in the D&D world!
*cries*
