My two cents.
Khan is as fast as anyone else out there, if not faster. He has a huge advantage with s hand speed. He is also an accurate puncher, and has decent power, he marks his opponents and in most of his fights you tend to think he'll get the knockout inside the first 4-5 rounds. Unfortunately his boxing brain is rubbish and hopefully is something his new trainer will sort out. Instincts are instincts though and I'm sure he will get drawn in toe to toe again the future at which point he will get hit and lose his 'game plan' as he does.
Regarding his chin- ok so he gets knocked out, and pretty spectacularly. This doesn't mean he necessarily has a glass chin. He actually takes a lot of shots. Best example being vs Maidana who is widely known to be a heavy puncher. He took a lot of punishment in that match. Ok he hasn't got a granite chin like Carl Froch, but he can certainly take some hits. Ricky Hatton has been knocked out badly, does that mean he has a glass chin? No.
On paper Khan should have what it takes to beat anyone in the division. Hopefully Hunter can actually make it happen. I think he'll beat Garcia in a rematch, providing he sticks to a game plan. Even in the first fight, Garcia was clearly struggling to keep up, and was getting caught all the time, before he finally landed on Khan.