We get deadlocks every once and a while as well. By any chance are you doing any SQL replication? We thought this may have something to do with it or at least causing more deadlocks. We are trying replication even though I am not sure it is supported for EV databases. For sure do not do replication on the Compliance or Discovery DBs. I have had problems with Compliance and Discovery upgrades if their DBs are setup for SQL replication.
Unfortunately, I don't have a great answer. This link helps describe deadlocks it is possible that it is the application.
http://www.sql-server-performance.com/deadlocks.asp