I think that "time to throw" stat is somewhat meaningless. Cross reference that with sack totals and it doesn't mean that a QB holds onto the ball to long in some cases. Case Keenum holds the ball for 6.77 seconds on average, but has only been sacked 20 times and hit 68 times. Eli Manning (bad line right) holds the ball 2.53 seconds, but has been sacked 29 times and hit 62 times. Russell Wilson holds the ball almost longer than anyone (scramble much) 3.05 seconds and has been sacked as much as Eli 30 times, but hit 99 times.
Meanwhile Bronco QB's are in middle of the pack for holding on to the ball, but in the bottom 5 for sacks (41 with 84 hits). The time to throw stat doesn't include sacks which would lower the number.
My guess is that our QB's are either having a hard time finding an open receiver, either not open or they are not seeing it, and we have a line that has a hard time protecting them. If we had a scrambler they might be able to make plays with their legs or by extending the play. Or if we had a really good pocket passer they could make plays by getting the ball out of there quickly and reading the defense better.
I just think that you can get a slightly better passer, better system, and a decent OLine and you could be performing like the Vikings. Is Case Keenum an elite QB?