Really, I guess that's why the recruiting services have him in the top dozen at his position.
And why he has offers across the nation from:
USC
Alabama
Arizona
ASU
Auburn
Boise St
California
FSU
GT
LSU
Miami
Michigan
Missouri
Nebraska
Notre Dame
Oklahoma
Oregon
Oregon St
PSU
Stanford
UCLA
UW
Look at that list of offers from a variety of offenses, Pro-sets, Spread, and an OPTION attack. When did Stoops, Saban, AND Paul Johnson suddenly take an interest in slow, meek OLs? Perhaps they saw his nimble feet (for a big man) as one of our poster's here who actually saw him play in person noted.
Banner has a wing span like a 747 and you're going to gripe about his speed because he doesn't move like a F-15? In a pass attack all he has to do is hone a quick drop back step. With those arms DE's are going to have a lot longer path to the QB than they will through a small OT and they aren't going to bowl hiim over.
It's common for OLs not to show a mean streak because they didn't have to in HS. Most are so much bigger that they dominant through sheer size. Speaking of mean streaks, list the ND OLs who have demonstrated that on the field since Jeff Faine. (John Sullivan angrily snapping the ball over the QBs head doesn't count.)
Clark, you wouldn't have refused a scholarship to Luke Petitgout out of high school. He was a TE when Holtz recruited him. 5 years later he was the 19th players chosen in the NFL draft. Banner may never do that well but he ain't "bad".
With the limited scholarships USC has available they aren't wasting one.