Edit: Sorry, didn't mean to sound harsh, 7 hour drive left me quite tired and its 3 am almost. That and every time i hear "Oh, (assassin) is OP" it upsets me. Yeah, the ADC with 0 bonus health and 30 MR should totally out preform the assassin, along with every other role in the game. Assassin's are the only (and best, 2nd being hard initiation like malphite ult... which is kinda assassination) way to counter ADC's late game. But they do their job too well and have gotten too nerfed.
Seriously, I'm tired of people complaining about assassins. They killed you 1v1? You're a squishy mage mid? What did you expect?! I am MUCH more scared of a Akali, fizz, or Leblanc mid. Why? They're designed to kill squishes, Aka yourself sitting in mid lane. They have MUCH higher damage, WAY better escapes, and don't have the mana problems diana has... nor can you dodge their harass.
I love playing assassins. Favorite role. I'm tired of people complaining they do too much damage. Diana has some of the biggest (and only) mana problems of all the new champs. This is her weakness. She's poking you with Q? Watch for the animation and move forward as soon as she casts it. Even if you can only dodge every other Q you'll survive and she'll be out of mana. You also can't let her out trade you. She's just as squishy as you and has to get in melee to use 4/5 of her spells (passive). Leblanc will shut her down. Malzahar will. Brand will. Ryze will. But any squishy/non-assassin? If you face tank every Q expect to be killed. If there's ANY assassin mid swap with your brusier top and enjoy the free mid lane. Counters exist in this game for a reason x-x
Tl;DR: Rock is calling Paper OP while saying Scissors is perfectly balanced.