You can skip to the last line if you want my most direct opinion of Miles without the diatribe.
Miles isn't on the hotseat because of wins and losses outright. Previous posters have mentioned the embarrassment of riches in the talent department that he has seemingly squandered, but I don't think this is the primary reason for the pressure.
Rather, Les Miles has a well documented history of beyond questionable game management. Here's a link that does a pretty good job of documenting his terrible decisions through 2007 (warning: obscene, albeit seemingly justified, language ahead):
Did they really just do this? Les Miles Syndrome. - Shakin The Southland
This list doesn't even begin two of his most egregious coaching atrocities:
1. The 2007 LSU-Auburn game where Matt Flynn fortuitously threw a 22 yard touchdown as time expired to give LSU the victory when a field-goal would have sufficed for the win
2. The spike that Les Miles called against Ole Miss, causing time to expire and costing his team a chance at winning. Afterward, he attempted to shirk responsibility, denying making the call himself and denouncing the decision as wrong. Predictably, video almost immediately surface showing Miles furiously making the spiking motion before the play. This is the worst coaching failure that I have witnessed. This call was an epic failure from a the standpoint of coaching fundamentals, intelligence, and personal integrity.
In short, Miles is a complete buffoon. The only thing keeping him employed is the dumb luck that led him to a national championship, and apologies for further sidetracking the thread. Richardson would be a huge get, but he seems bound and determined to leave the state.