Who is doing the picking?
Here are the guards we recently drafted:
3rd Jared Wilson
3rd Caeden Wallace
4th Layden Robinson
4th Jake Andrews
4th Sidy Sow
5th Atonio Mafi
1st Cole Strange
6th Chasen Hines
6th Mike Onwenu
7th Dustin Woodward
4th Hjalte Froholdt
Some of these guys are doing really well for other teams (Andrews, Strange and Froholdt) but we've expended a whole boatload of resources to end up with only Onwenu and Wilson.
In retrospect, letting Strange go was a big mistake because he did pretty well for the Dolphins and even rose to becoming captain for them. They are going to keep him.
The problem I see with your analysis is that 4 of those players were drafted for other positions not for guard.
Jared Wilson was drafted as a Center. He was put at guard, in theory, because he was the best option.
Caeden Wallace was drafted as a RT.
Jake Andrews was drafted as a Center who showed enough under BB to get some snaps at guard.
Dustin Woodard was drafted as a Center. This was a miss, in general, since he retired before stepping on the field.
You're going back 7 drafts and ignoring the low success rate of players in the 5th, 6th, and 7th rounds. Of the 11 you listed, only 7 were drafted to be guards. Of those 7, Mafi, Hines and Onwenu were drafted in the 5th round or later. 1 in 3 is actually far above the success rate for those 3 rounds.
Robinson, Sow, and Froholdt not working out are the bigger misses oustide of Woodard.. Froholdt took years to find success and a position move.
I think that Vrabel will ask himself what they missed in their evaluation of Jake Andrews that caused them to believe they needed to add a Center/Guard in the Draft. They'll probably self-evaluate on Strange as well since he only gave up 2 sacks, 3 hits and 16 hurries whereas Wilson gave up 8 sacks, 7 hits, and 26 hurries on the season.
Guard is one of the positions you need to be looking at yearly in the draft. Just like Corner. In my opinion, 1 OG each year for 7 years with 3 of those picks in the 5-6 rounds isn't bad. Even if you going with 1.5 picks by saying the Interior, I'm not sure that 11 picks over 7 years for 5 positions (3 starters/2 backups) is a lot..