Joe Flacco was sacked 35 times, and is listed as having 32 rushing attempts. Even if he might have scored or ran out of bounds on half those rushes, that's 51-67 times he would have been taken to the turf by a defender.
Russell Wilson was sacked 33 times and had 94 rushing attempts. Again, giving him maybe 1/2 those rushes where he might not have been tackled, that's still 80-127 times he WAS tackled.
There's just no way I can see where a QB who's getting planted in the turf nearly twice as often (usually by 250lb LBs or 300+lb linemen) isn't going to be more injury-prone.
Not to mention that QBs like Flacco/Big Ben can take more hits in general due to their large bodies. Running QBs are generally smaller