I think if you want a fast, atheltic QB who can throw the rock and completes at a higher percentage than Dixon, you wait a year and take Pat White next year.
Wait until next year. 1st round next year draft the RBOF and if ML can't get it done this year the Cards need to seriously start thinking about getting a QB (probably veteran) that can "win now" with this talent base. I'd hate to think about taking a QB in the 5th in the hopes he can turn out good 3-5 years down the line if ML doesn't pan out. This team is MUCH too talented to be hampered at the QB position.