Paraxis: What about my Roy-the-Warlock example, in which we postulate that someone's in this bind not of their own choice?
A concept like that is workable, but hard to roleplay. A character who's parents sell his soul before birth (let's assume they can), and grows to develope power from that is not Evil himself everything was out of his control. But to further develope those powers knowing the source might be a different matter. Back to the Elric example, if you forsake the power and take levels in other classes thats one thing, to keep taping into the power to try and do good is balancing act I think. One that could be cool to roleplay out.
Take Spawn for example, in the heat of the moment of death he reaches out and says he will do anything to go back so he can be with his wife. Selling soul = evil act...now he is not an evil person from that one action (let's ignore the whole he was a government assassin), but he is stuck. He can't change class for example in the comic, but he can try and control and limit the use of his power and for a good long time he does exactly that.
But all that said, I still think the overall tone of this class so far is very evil, no matter the alignment requirments.
So yes you can make a repetant or forsaken type good guy, or maybe the shadow and feral powers are going to be Good and have related powers. But from all the fluff we have so far the class is very Dark and mostly Evil.
Again, a favored soul/warlock class or just sorcerer would have been a better build then this warlock class it looks like we have been given.
The whole Evil thing about pride and letting some of the orphans die, well thats how life works. It's exactly the kind of tests that dieties in real world religions due all the time, the paladin doesn't have much faith in his god if he thinks he needs to have a demon bail him out of the situation.
EDIT**added this next part.
And you are certain that Mr. Warlock cannot get more powers from their class if they solve puzzles, beat traps, overcome RP encounters and don't kill their opponents?
Because if you are, I'd like to see your advanced copy of the PHB.
The problem isn't killing for XP, it's that they have a class ability that only works if they kill someone they have marked. So they get a power from taking life, a power not XP, someone else started comparing a fighter gaining XP from killing so he must be Evil. Well no the fighter isn't evil for getting XP, but a Warlock that targets a creature for death then gets some ability for slaying it is.