Couple thoughts about couple champions.

Annie. As Annie player have to say she's powerhouse right now. She's tanky, has huge damage and nice mass control abilities. While most midlaners suffering from manaregen nerfs, she doesn't care about mana and can farm until her jungler come to gank. Most old counters dont work anymore because they have to choose: use mana for farm or for poking Annie. Mobile, not so mana dependant champions will work against her, but later she will be unstoppable anyway.

Leona. Leona is one of reasons why I stopped play botlane (second is Thresh) in season 2014. One of most tanky champions in game, tons of control and nice damage. Honestly I think that good Leona has no counters (except Morgana). May be it was Lulu with polymorph. Now with Relic Shield's healing Leona can do not worry about any poke, and nothing can stop her. In previous season Morgana appeared mostly as an answer to domination of Thresh and Leona. Later ADC was hardly buffed and ADC oriented support came back, but now Leona came back.

Blitz. His damage is too huge, so my friend even playing him on top lane.

Heimer. He's my supermain. He's too situational. Depending on combination he can be unstoppable machine or useless fat minion. When I'm playing him, and I see right combination, it's 95% win. I had many games where my team was losing 20-40, but we won, because we had right combination. When I'm talking about combination I mean my team champions and enemy team champions. Perfect combo when they have dive oriented team and Heimer has team with some long range champions, and with some AOE CC. Worst combination is when they have AOE CC + long range or burst, and when Heimer has mobile team full of assassins. I think that hot & cold style is unhealthy. Sure, champions must depend on combos, but not so much.