Ok first off, yes straight ap is dead BUT his AP scaling is really good. I made a new strategy and build that is so good to utilize boxes early game it's ridiculous with this new rune system also high-risk high reward Shaco style is back I main him top. AP Lethality build is basically all AP items with Duskblade to utilize the passive scaling you get with backstab and E ap scaling. With this rune build Shaco boxes after hitting the enemy champ 3 time with the additional damage boost will destroy mostly any top early game. Also I always steal red/blue before going top lane. Start off with dark ring and either start building duskblade first or nashoor's tooth for a quicker 3 hit damage amplifier. If you snowball and get enough stacks I usually replace boots with Luden's Echo.
Been using this AP lethality build before new rune system, but now that rune system doesnt give you armor and magic resistence right off the bat, boxes can shred hard early game.
The Adaptation runes work depending on what your items give more of ad or ap so I really dont have that problem when I get dark ring at the start of game it gives me AP.