Diana attack speed is OP, but I feel you are dooing it wrong, I personally feel the best way to build her is Sorcerer's Shoes/Mercury thread, Malady, Wits end, Frozen hart/RCS/GA, Lich bane, Bloodrazor. My thought process behind building her Attack speed/Magic DPS is to get the most out of her passive (as combined with the tankiness from all the MR/Armour I use in my build and runes) combined with her Q-R-E combo and AOE stuns like Annies tibberts you can quickly dish out amazingly high damage without the enemy team being able to do anything, however I do suggest you hit with you q before diving in as having the ability to quickly escape to a minion or jungle creep in front of the fight can be the difference between a suicide dive and surviving the fight.