Recently, AP Tryn w/ max CD reduction was very scary, but now that his Q has been nerfed, I'm not sure he works anymore. Supposedly, it was a theme popularized by one online individual who lifted himself to at least gold ELO playing nothing but AP Tryn. It received even more news when Riot said they'd be nerfing his Q's AP ratio.
With AP Tryn, his farm clearing was insanely fast (could kill a minion line in one spin if his AP's high enough), he could quickly spin through most terrain (also helped farm jungle creeps faster), his Q recovered +50% of his health, his W benefited his entire team's chasing potential, and of course, his ULT gave him a 2nd chance at life plus a max fury bar, meaning another +50% of health pop after his ULT wears off. With 40% CD reduction, his ULT max level was at 54 secs, so it was up on nearly every team fight.
Even with bad early farm, he can snowball into a CS lead later as he spins through the entire jungle. Caught in opp's jungle?... No problem, spin through the terrain! Caught again? No problem, it's on a 5.4sec CD max lvl w/ 40% CDR, so spin through another set of terrain! Caught some more? No problem, pop his ULT to buy more time for another CD on Spin! He is a beast at going wherever he pleases.
Tryn in pub stomp at low-mid ELO was really scary. Now with the Q nerf, not as much, since his laning phase will be too heavily impacted. Due to his fury reliance, he has to go in to hit minions regularly, but he cant do that if he's getting bullied out of lane, which he likely will be.