Pros:
1) Easy to understand now, no questions. Really good for casuals and those not wanting to worry about number crunching.

Cons:
1) It removed a huge chunk of skill required. Learning to manage hate, either holding it on limiting hate on a DD job while dealing the most dmg possible was something that separated a skilled player from a noob. Aka this is a easy button bad for hardcore ppl.

I see this as a major negative, but the only negative to the whole planned battle changes. And those saying just have a turn off option. Well if it is there people are going to use it, those not using it will be reamed by their guilds for not performing at optimal efficiency.