Despite the increased usage of Mr. Mime, I still run Landorus EX in 2 of my decks: Big Basics with Garbodor and Empoleon. In matches where I run BBwG, Mr. Mime is a non-issue - Lando still performs quite well with the 30-30 damage output. With Empoleon, should my opponent have a bench-protecting Mr. Mime, I still find Lando quite useful, especially when my opponent declares, "I did not see that coming," an unexpected Land's Judgment attack.
On the other hand, Empoleon deck usage has also increased given recent tournament successes. Empoleon's somewhat "easy" ability to 1HKO a Landorus EX may have decreased players' interest in running Lando too.
Needless to say, running Landorus EX effectively and successfully is highly deck-dependent (like any Poké). For me, I will still use it where it "fits."