So this is my Tank/ap build , Its meant to be played as a support , not a carry so try to only get assists not the kill , if played right you should be dominating with tons of assists and few deaths.

This mastery build i go 9-21-0 starting with one point in cripple, which is a must if using exhuast. I then put three points in Archmages savvy which simply increases your ability power. 4 points in sorcery to decrease cooldowns and 1 point in sunder to help when auto attacking. In defense i put 3 points in resistance to increase magic resist, 3 points in hardiness to increase armour , 2 points in strength of spirit for the much needed health regen.