Frankly, there is no player in the last 15-20 years that I can remember who created this much of a stir when they came back. TO did but for very different reasons.
These are the principal questions:
1. Did the Eagles make the right move in letting him go last year? - At the time, I would say 'yes.' Putting the emotional issues aside, his performance had diminished last year. I imagine the capper for the Eagles was Dawkins weak playoff performance and his pretty poor game in the NFC Championship where the Cards notably picked on him in coverage a few times. If the defense and Dawkins had played better, they might have been more inclined to bring him back. Hell, even JJ admitted last year towards the end of the season that he had changed his schemes around to bring Dawkins up to the box more and took him out of most deep coverage responsibilities. Places an awful lot of stress on everybody from the defense coordinator on done to have a FS who is an acknowledged liability in coverage.
Dawkins did a get low-ball offer from the Eagles to comeback but even the most ardent Banner/Reid haters would have to acknowledge that this team has been pretty damn savvy about knowing when to get rid of their veteran players. Hell, the only veteran during Reid's entire tenure you can make a legit case that they made a mistake on was letting Trotter go to DC. It was more a money thing though because the Eagles didn't want to tie-up so much money in position they deemed of secondary importance (MLB).
Everybody harps about the '5-year deal' but that is missing the point. Eagles didn't think that Dawkins was worth making one of the best-paid FS over the next 2 years. Broncos did and Dawkins jumped at the money.
2. Did the Eagles make the right move judging how things have played out this year? - In retrospect, I would say the Eagles' made a mistake with Dawkins. Apparently, the Eagles did miss Dawkins leadership abilities and his play at FS. Didn't readily acknowledge that they brought back Trotter for his leadership on & off the field qualities but it did come out later that it was one of the reasons that Reid brought back Trotter vs. pursuing other potential options at MLB. Defense struggled the first few weeks and it did seem like it had a bit of an identity crisis with a new coordinator, Bradley's injury, etc. Don't know if Dawkins' leadership qualities would have made that much of a difference but I can't imagine it wouldn't have been a bit of a boost.
More importantly though, the Eagles have missed Dawkins at FS this year. None of the 3 players there (Harris/Demps/Jones) have shown that they are capable of being a full-time starter . Jones has gotten the most playing time at FS this year but it is largely because of his veteran status. After an initial high level of play in his 2 two starts, Jones has really leveled off it seems including showing some really shoddy tackling the last 2-3 weeks. Demps thinks he should be the starter but he obviously hasn't shown the Eagles enough since training camp to gain the spot outright as a starter all season long. Harris was named the initial starter out of camp and has seen some additional starting time there during the middle of the season. Opinions seems to vary on him including how scouts thought he performed very well in the Falcons' game against Gonzalez to getting abused in the 2nd 'Skins game when pressed into duty as a nickel corner. Overall, it hasn't been a position of strength for this defense all season long ridiculous of who has been out there and McDermott is likely to remain shuffling Harris/Demps/Jones around for the remainder of the season.
I haven't watched many Broncos' games this year but the reports & stats seem to indicate that Dawkins has played at a pretty high including providing his usual strong tackling. If there is anything that this defense has missed, it is Dawkins' ability to tackle in the secondary and ability of the Eagles' to get pressure from their secondary when they send them on a blitz package. It is hard to believe that Dawkins wouldn't have outplayed the Jones/Demps/Harris trio so far this year.
3. Most importantly - would having Dawkins on this roster made a difference in the W-L column? This is probably the most difficult to judge because of the impact of any one defensive player on the outcome of a game. Looking at the 4 Eagles' losses this year (NO, @Oak, Dal, @SD), there is really only one game where I can see that Dawkins might have had an impact - SD. Dawkins might have been able to provide some leadership to a defense that played a very lackadaisical 1st half in SD and struggled to stop LT when they needed to/get some pressure on Rivers. Can't see what difference Dawkins would have made in the other 3 games because he wouldn't have provided enough of a difference in the Saints' game and the defense really wasn't the issue in either the Raiders' or Cowboys' losses.
IN summary - Eagles have missed Dawkins at FS this year because of the average/below average play of the Jones/Demps/Harris trio but I really don't know how much more of an impact that having Dawkins back on this roster would have been made in the W-L column to date. Maybe the SD game but not bringing back Dawkins certainly hasn't been the end of the world either.