Two Massive Problems with S5
Dragon:
Dragon buff is incredibly powerful now. It seems like the entire game revolves around killing dragon. Most team fights dictate who gets it and then this determines who wins the game. The game feels really dull now because if one team gets 3-5 dragon kills its basically a loss. Comebacks are less likely due to snowballing of dragon buffs. The game should revolve around big plays and team fights, not who kills the NPC.
Jungle:
Jungle sustain items are terrible. I don't even know if they're worth making anymore past starting machete. This also greatly reduced the number of jungle champs. Another change that has really restricted and simplified gameplay. Jungle ganks are also less common than ever. So far the only viable successful jungles I've seen are warwick and that about covers it.