Of course they needed to upgrade, but the question is was it worth having to let good players go and start over having to focus so much of our draft and free agent attention on converting to 3-4 when perhaps we could have just kept the 4-3, picked up a few players needed to put that scheme on track .....
We certainly wouldn't have needed to draft or otherwise acquire 11 D-linemen and LB's if we had stayed in the 4-3. Maybe 4-5 D-linemen and LB's would have done the trick, and we could have had the resources needed to upgrade the O-line and FS positions as well.
In other words, don't look at it just from the standpoint of needing to upgrade the defense either way, but also from the standpoint of what, if anything, it cost us in the overall picture.