Somebody did the math on that and found it was still much too strong at high levels.prof bonus per day sounds a nice middle ground.
I haven't checked those calculations, but they fit with my experience playing a warlock under this house rule from levels 11-15. Two short rests per day was plenty -- I had no trouble at all keeping up with the other PCs, all of whom were regular full casters (wizard, sorcerer, and cleric). If anything, they struggled a bit to keep up with me.