Retina MacBook Pro - External display resolution issues
While this might not provide a direct answer to your question, I would be interested in the EDID (Extended display identification data) of that display.

Run ioreg -l | grep EDID on terminal to get all the EDIDs listed. Your output then includes one line for each display connected, such as "IODisplayEDID"  =&lt;00ffffffffffff000...&gt;. Take the part in between &lt;and &gt;, that is your edid.
Note that the short EDID/the first one is probably the one of your internal display, which has no resolution information on it.

Now you need something to read out the EDID, I used the http://www.edidreader.com website. Unfortunately they require the hex to be split and prefixed with 0x. Ruby to the rescue! ruby -e 'puts "0x" + ARGV[0].scan(/.{2}|.+/).join(" 0x")' 'YOUR EDID HERE'.

The EDID contains multiple blocks of possible resolutions, called timings. They can be found in 


Timing Bitmap
Video Data Block
Detailed Timing Descriptor #


Does the display offer proper resolutions? Can you try with a different cable or a different machine?