Changes to Baron and Dragon
Baron and dragon are no longer optional. Thanks to the changes made by riot the buffs given by baron and dragon have been readjusted in such a way that now every team fights for them. While these buffs grant you strategic advantage in the game, it does not mean you will dominate. The other team can over-power you by building different set of items. So, baron and dragon buffs though are essential in attaining objective but should be utilized wisely to get the most out of them.
Dragon used to provide with nothing but gold for each of the team members. This might seem as a major advantage but have 200 plus gold was just not exciting enough. Riot has changed the dragon buff completely. On killing the dragon for the first time you get and AD and AP increase. On second kill you receive a buff which deals bonus damage to minions and monsters. Third dragon kill gives your team bonus movement speed. Fourth kill allows your team to deal bonus damage to turrets and inhibitors. On the fifth kill all these bonuses are doubled and your attacks would deal true damage to enemy champions for over 5 seconds. These buffs are permanent throughout the game and are global. The con is that dragon does not give the global gold anymore, however the killer of the dragon does get some experience and gold.
The global buffs provided by baron have been revised as well. When baron is killed your minions would become stronger in the presence of an allied champion who has the baron buff. These minions deal greater damage, travel faster and sustain a decent amount of damage. Furthermore, baron provides an extra 40 ap or ad buff to the killing team. Imagine having taken down an enemy inhibitor and then killing the baron, you would be storming the enemy nexus turrets with more than just super minions.
The above changes might not sound exciting in the case of baron but for dragon things have changed. Teams fights over dragon have become common. As a matter of fact, team fights often start while keeping vision over dragon, especially while killing the scuttle. Here is a fun fact, the scuttle not only provides vision but give a temporary movement speed buff to allied champions when they cross over it.