Right... Because Tryn and Darius have no counters right? They never lose? You're clearly just an angry person. I don't own Darius and despise Tryn, but they are easy to beat. Tryn on the other team? Oh man one frozen heart or Omen on your team and he's shut down, poor little Tryn Darius is a little insane right now but he's getting nerfed anyways. You cannot name a single Champion that can't be countered.
Darius... yeah, not much can be done there.
"OP" dream team. Trynda, Darius, and Jax. Perfect balance of physical and magic damage. And of course that old fashioned "We must pick stronk or no can win!" mentality. I would DARE someone to threaten "Just pick a ranged carry and that composition is easily countered" and then try it. Too much slow/spin/leap/stun/grab/slow again for anyone to handle.
As for the original poster, don't yell at RIOT, yell at Morello. He is the final say on releases and on several occasions he has released a champ firmly stating they are balanced only to get a hot fix within the week. He's known for it, he loves to do it, and also keep in mind.... IT DRIVES SALES!
The game is kinda old now. Most players have all champs/runes or at least many of them. Making the new champs overly strong at release is a way to generate funds. Not because old players blow cash, but the little kids who aren't good but CAN be with just a few dollars pumped into RIOT certainly do. It's all about the money.
EDIT: As for a little backup on the Morello topic, anyone here remember Xin Zhao upon release? Yes, according to Morello, Mr. "I can easily 1v5 with little to no farm" was balanced. Same was said with Riven, Hec, Lulu, Darius and a few others.