Well, I think he is better than you give him credit for. When he went quiet after the fight with Nickels, he was hurting bad. Don't forget that he received a medical suspension after that fight.
In regard to his upcoming fight with Bisping, I think he has a good chance. He is a much better wrestler than Bisping (as evidenced on the show, remember Bisping complaining about hard Hamill was working him during training?) and his standup is good enough to at least defend Bisping's striking long enough to put Bisping on the ground over and over again.
Bisping might just KO him but Hamill will own him on the ground.
I have read recent statements from Bisping about how he thinks Hamill is a lame duck of a matchup for him and personally, I think he's just scared to be up against the one guy in training who could really throw him around.
His helmet was stifling, it narrowed his vision. And he must see far. His shield was heavy. It threw him off balance. And his target is far away.