The only problem I see with this is the 13 damage. The pregen paladin's mark only does 8, which is enough!!
I think you could run the skeleton either way. In general, I don't think skeletons place any value on their existence, so they are okay with suicidal orders. But an ooze for example, which is really dumb, still would quickly learn that certain actions are bad.
Now if golems are still mindless, it should be willing to attack your warlock everytime.
As for the undead and charms argument, it makes perfect sense to me that undead are vulnerable to charms. Consider that in dnd you are dealing with completely alien mindsets (aberrations for example). I mean, an undead's mind is likely not that far out there. In fact, in some ways an undead mind could be easier to influence. Their mostly instinctual (at least the base level ones are). You know, kill kill kill. Think about having to use magic to subvert all the complexities and intricacies of a mind flayer's mind?