You know, for as much as I don't think that Smith can get us to a superbowl, he's not the one to blame for this season. This season falls on Dimitroff.
Dimitroff's drafting has put the team in a very bad place. You know that I feel that the move for Julio was a bad move. The principal argument that it was a good move is that Dimitroff wouldn't have done better with the picks we gave up. Either way, Dimitroff isn't very good.
He also tends to draft injury prone players. (even knowing that they are injury prone) Julio Jones, Peria Jerry, Sam Baker, and William Moore were all high picks used on players who were injured the year that they were drafted, and who have continued to have injury problems since they've been in the NFL. Weatherspoon has been an injury waiting to happen... Ewing has been on IR for all but one game of his two year career. This is a significant trend.
Dimitroff completely missed on Ray Edwards. Giving a big contract to Dunta Robinson also wasn't the best move. Nor was giving a big contract to Sam Baker or Justin Blalock. (both of whom are average at best) Bringing in Jackson didn't seem like the brightest move considering the apathy towards improving the offensive line.
Generally speaking, Dimitroff has overpaid for average and OLD talent, and hasn't been able to acquire really good talent through the draft, outside of Ryan and Jones. Dimitroff might not be Blank's first target, but he is the biggest problem that we have at this point.
While I agree with the gist of your post, the part about injuries I have to disagree with. Moore isn't injury-prone because he was nicked up a couple of times in college. He's injury prone because he plays safety. Look at Malcolm Jenkins, who was as durable as they come at Ohio State, has missed 10 games over the past 4 seasons because he plays the safety position. Running Back and safety are the two positions that have the shortest shelf-life in the NFL and it's just the nature of the position. When a player like Lawyer Milloy emerges (only 6 missed games due to injury over a 15-year career), that's an anomaly, not the norm.
You can't really blame GMs for injuries. Now in the case of a player like Peria Jerry, it doesn't mean you don't draft him. It just means you don't draft him as high. When you have the specific injuries that Jerry had: all lower body injuries which suggest that he's carrying too much weight (see Byron Leftwich), it should have lowered his grade to an early-to-mid 2nd round pick at best rather than a late 1st.
Julio on the other hand was such an enormous talent that the nicks that he suffered throughout his career at Alabama were easy to overlook.
Baker was beat up at USC as well, but that wasn't the mistake. Again the mistake was taking 5 lackluster seasons and rewarded Baker with a market level deal that the Falcons couldn't get out of until Year 4 without greater consequences. Everyone understands why the Falcons opted to take Baker instead of a player that ultimately proved to be better in Duane Brown. Baker was deemed more NFL-ready. Again, the mistake was after 2010, the Falcons should have realized then that Baker was a poor fit in the blocking scheme (he was a zone-blocking guy at USC) and his inconsistent play merited the team looking in a new direction. Unfortunately because of the Jones trade in 2011, the Falcons didn't really have the opportunity to draft an insurance policy. But then after the 2011 season that Svitek had (essentially showing that Baker was expendable), the Falcons then drafted Lamar Holmes in 2012 as the insurance policy and Baker had his best year. Re-signing Baker wasn't the issue. You want to reward solid play and faith, but the team should have signed him to a much more team-friendly contract, otherwise they had his replacement in house with Holmes and could've easily re-sign Svitek, or signed a FA like Anthony Collins or King Dunlap to be the insurance policy behind Holmes.
It's the compounding of mistakes that TD has messed up on. Again, trading for Julio wasn't the mistake. It was drafting a bunch of at best complementary players with the remaining picks that was the mistake: Ewing, Mitchell, Dent, Holmes, etc.
The Falcons did not have strong drafts in 2009 and 2010, and thus needed to have stronger drafts in 2011 and 2012. Giving away those picks was a bad strategy in the sense that it lessened the chances that they could have those strong drafts because they basically dealt away half a draft class. But they still had the opportunity.
Imagine instead of Akeem Dent in Round 3, the Falcons had gotten Justin Houston, Jurrell Casey, or Cecil Shorts-type value with that pick. I'm not saying that they necessarily picked those players, but instead had picked some player that had returned similar value with that pick.
Or in Round 5, instead of Quizz, they got Denarius Moore, Julius Thomas, or Richard Sherman.
In 2012, instead of getting Ewing, Mitchell, Massaquoi, and Robertson in terms of value, what if we had gotten Alfred Morris, George Iloka, Danny Trevathan, and Billy Winn?
It's also interesting to look at the success that players such as Darrin Walls, Chris Owens, Brent Grimes, Vance Walker, John Abraham, Curtis Lofton, Harvey Dahl, and Eric Weems have had or are having since leaving Atlanta.