Im sure they are around but I have never heard of them in my 5+ yrs of playing. I could have missed them due to how fast linkshells seem to come and go.
One of the things about all <insert job here> LS's is that generally you don't find a lot of people end up in the shell leveling the job that the job is listed for.
Of the few types of shells that do survive, All BST shells generally work because it gives bst's a chance to do offer support and do missions in odd but fun ways/ Bsts tend to get frowned upon for missions because people don't consider them the end all in DD as well as doing a lot of things on our own. For a while Lotb was organizing all bst CoP runs which turned out to be really fun. 6 Bst together is a force to be seen. 15+ bst is a blast.
Smn shells work for the same reason, people helping each other in ways other than making them just another whm wannabe. Helping with the camping of NM's that most people wouldn't help with because the gears only good for smn.
Some shells even have gone as far as going to Pet class based (so Bst, Smn, Pup and in some cases Drg (although personally I consider the wyvern to be too stupid to be really called a pet, more of an extention of your job)
The only other Job type LS that I have heard of is a Blue Mage LS which of course has the advantage of having others that can help you get the spells that you need. Its something in place to support each other.
Most other types of jobs are common place and usually theres nothing that specializes them from another DD, Tank or Support.
Although with the latest stigma against blm's I could totally see a blm LS working. :)