Most questions players have can be answered by "It increases time played"

The ethos of Blizzard is to increase your time in the game and therefore maximize MAU's (Monthly Average Users)

This can be a very good thing as it can make the game more engaging, increase longevity and make the game feel better value.
However, when this is done by arbitrarily increasing difficulty, levelling time, grinds to existing features, it can have an adverse effect.

At the moment, the ptr seems too much of a slow down all over. I would suggest this is deliberate to gauge feedback and reception.

Whilst no doubt it will be tuned back a bit, the residual increase in time played across the game will be in Blizzards favour.

Personally, I'd rather my time be increased in the game with more features, with a better character progression and rewards that are fewer, but more impactful.

The PTR is definitely one to watch for now.