You skim over the armor proficiency like it's nothing. But armor matters a lot to a melee warrior. Campaigns in my group are pretty combat-heavy, and we have a practice of "fight clubbing" newly created PCs - we stage a mock combat, then allow people to rebuild their PCs afterward, so everyone can be confident that what looked good on paper actually plays well in battle*. My hexblade's starting magic item was a broom of flying, but after the fight club, I swapped it out for a cloak of protection. Getting +1 to my AC and saving throws was that valuable. And that decision has already made a big difference in play.Not really. See sure they get profiency in medium armor and martial weapons, but martial weapons is pretty moot if you're going pact of the blade. CHA bonus to attacks and damage is cool, but really what does that add up to, 1-2 or difference at best.
Each point of AC effectively boosts your hit points (each time a monster misses you with an attack, it's as good as being healed for the amount of damage the attack would have dealt), and increases your chances to hang onto concentration. Regular warlocks have neither medium armor nor shield proficiency, and that is absolutely crippling for a front-line fighter. Hexblade would almost be worth it just for the armor and shield. Everything else is gravy.
[size=-2]*Yes, I know, we are a bunch of mouth-breathing roll-players, et cetera, et cetera, et cetera. Whatever. I can't dispute the point right now, I'm busy playing referee while my dead sister's soul bound into the cloak of protection argues with the diabolic spirit that animates my pact weapon. They can't agree on what to do with the slave I rescued in the last adventure, who has become a touchstone for my character's demented commitment to helping the innocent. Also, the city that serves us as a home base is morally abhorrent and I may have to start a revolution. Having a decent AC is really helpful in revolutions.[/size]