Honestly, I really don't think there's enough to question the guy's arm strength. He's thrown some pretty touchdown passes to Evans (not just this year, but last year as well...he had a beautiful one to Evans against Miami) that required no slowing down on anyone's part.
It's all about the timing, not arm strength. Repeat after me.
Nobody questions Brett Favre's arm strength (particularly in the past) and a ridiculous number of his TD passes required his receivers to slow down and go for the jump ball. Timing, not arm strength. And in some cases, it's by design -- if the DB is not looking at the ball, the receiver can have an advantage on a ball thrown behind the receiver, especially the taller receivers.
Nobody question's JP's arm strength, but Evans sure had to slow down for that jump ball against the Jets last year. It happens.