As I said elsewhere I'm willing to believe that I'm wrong on this but in my experience I haven't seen anything broken about the Warlock class if you remove the Patron from the mix entirely. If you have a theoretical Patronless Warlock that has all of the abilities of a Warlock but the Patron never appears in their life to put demands on them, what makes the Warlock overpowered compared to a Wizard or a Sorcerer? I don't see it but I could be wrong!These forums are drowning in cleric/casters overpowered threads. The only thing that keeps pact casters from being overpowered The whole idea of pact magic is a deals a deal. You break the deal it sucks to be you.
It also gives players the ability to split hairs and do exactly what they are told even if it doesn't accomplish the goal or works against the patron. But you take away loss of power if they just flagrantly break the rules it simply gives the PC too much power.