First, every pick is unique. Trading down made the most sense for the organization, with many holes to fill and only 7 picks in the 2013 NFL draft. But it was a buyers market for teams looking to trade up. The Raiders went from the 3rd to the 12th adding a second round pick from the Dolphins. If the Jaguars did a trade like this and picked up DJ Hayden, we would have missed on a franchise tackle. So, the first choice of trading down was not as valuable as a franchise Tackle.
Secondly, I think that as a GM and fans we need to look at this as if this were 1995 and we just got the franchise. This team is going to be bad this year, we are poised to have another top pick in the 2014 NFL draft. Guess where the talent in the top of that draft is? DE and QB - Clowney - Bridgewater, Boyd, Fales, Manziel, Murray - We need to set up them for success.
This post is going to be under the assumption that the Jaguars resign Monroe at the end of the year (If we don't that is not a good call Mr. Caldwell), and Luke plays RT for the 4 years on his rookie contract.
Value for money - With the new CBA Luck will get a 4 year deal at around 22 million, which if my math is correct is around 5.5 million a year. The Jaguars can add a 5th year onto that contract. Lets say we resign Monroe at the end of the year for Jake Long money four years and $34 million, with incentives that might push it to $36 million. By the time Monroe is getting off of his deal Luke will be getting off of his rookie contract. Thus we can give him the big LT $ and have the tackle position solidified for the next 5 years, and LT for the next 8-10 barring injury of player bust. I would take that.
Is RT really that undervalued? I think sacks come from both sides of the line. At least that is what I heard. We play in a division where the best pass rushers come from the right side - JJ Watt and Robert Mathis. If we can have solid tackle play we can put more people into routes. This is so by far the most undervalued part of all of this. If a TE can go it on a route it puts more pressure on the defense and gives our QB an other option or out in case of pressure.
The Jaguars gave up 50 sacks - Gabbert was injured for a better part of the year for bad tackle play on the the right side of the line and LG. Who ever plays QB unless his name is Rodgers will not be that successful with those numbers. Why not put our next QB into a position with one of the better lines in the NFL it sure helped Kapernick and the Niners.
Onto Luke Joeckel. Luke was seen as the Top player in this draft, why are complaining about getting the Top prospect in the draft? I feel like the fans for this team have been burnt so long that we can't trust anything. With the Jaguars setting up a zone blocking scheme I think Luke is the perfect fit for this. His one "flaw" was that he was not your typical mauler tackle but in zone blocking you don't need that as much. He is a darn good football player basically. I don't think anyone is arguing that so I will stop there.
The only player that I thought we should have considered was Ziggy Ansah. I think he has the makings to be a special player. Dion Jordan made me nervous - he has a huge boom or bust feel about it. Both players would have filled a need but were not as good as Luke.
TL:DR RT makes sense because we had little choice elsewhere, our QB or DE of the future will be in the 2014 draft, and it isn't a big financial burden.