Is it a problem to have a large TempDB?
Important things :


Depending on your version of sql server, use TF 1117 and 1118 to equally grow all the files and alleviate tempdb contention. Those are safe trace flags to have. 
Make sure your tempdb files are all equally sized and set to grow by a fix MB as opposed to Percent growth. I would suggest you preallocate so auto-growth is minimal to none.


Followups:


Run sp_whoisactive @get_plans =1, @get_transaction_info =1 and log it to a table every 1 min or so and see the tempdb usage.
Tell the vendor to have application only get the data that is needed. Have seen vendors abusing tempdb, but once you highlight the issue they will hopefully address it.
Read fully - Comprehensive tempdb blog post series - by Paul from SQLSkills