I think he's overrated. His own head coach -- Mike Tomlin -- calls him "one trick pony" for a reason. The guy can fly. He can get deep. But that's pretty much all he does, frankly. His route running is fairly poor. He's a long strider -- not unlike Ted Ginn -- so he's not really built to stop and start quickly. As a result he rounds off his routes at times, doesn't run stuff at the proper depth at others. He knows what he does and hasn't put the time in to learn the rest.
You have to be able to run every route in our WCO. Everybody has to do everything, because versatility is unpredictability. Wallace doesn't do everything. He does one thing extraordinarily well (helped out by Roethlisberger, who's a top echelon deep ball thrower). That's a nice asset to have, but his predictability can be something of a liability.
Now, on the plus side I think the diva stuff is overstated with him and I think he has very good hands and I do love quick strike ability. But I'd rather rebuild the wide receiver position in the Green Bay mold, with guys like Jennings, Nelson, Cobb, Driver and Jones... who can do everything with some proficiency.
Look at our guys. Bess has no speed. Hartline is weak physically, can't sustain speed and has poor balance. Wallace runs most of the route tree in a below average fashion. If you're a defensive coordinator prepping his unit before you play us, you're basically able to tell your team how to read our mail. Bail coverage on Wallace (underneath coverage not as important since he doesn't run the comeback well). Bracket Bess with a corner and linebacker. And press Hartline all over the field. Done.