One of my favorite heroes in the game. Although his stats aren't great, his defense is really high for a Silvan, and his threat is low enough to fit into many hero combinations. I love pairing him up with Celeborn, and maybe even a hero like Leadership Faramir. Silvan allies can be pretty powerful, and this guy gives you access to out of sphere Silvans with the only caveat being once per round. The only downside is his weak will and attack, but that can be remedied in a variety of ways; although it might be best to just use his strongest stat and have him as a dedicated defender with some tweaks. An underappreciated hero that deserves some attention.
edit: I searched RingsDB and as of now there is only ONE deck featuring Thranduil. He really is an overlooked hero and I'd like to see some more decks and ideas with him; I'll be doing my part soon and I'll report the results.