The overall percentage damage increase of the two changes to haste and mastery vary depending on your levels of those stats. It's not possible to say how much you will benefit without inputting your specific values. I tinkered with WrathCalcs, and with 500 haste it's ~0.5% increase, and with 10,000 haste it's ~3%. As we're really only dealing with ~1,000 haste, it's safe to say it's around a 0.5% increase.
Mastery is a bit different. If we read the change as a 1/15 increase to the base amount of mastery and any other application thereof, then the damage increase will be equal to 1/15*(average mastery amount) per spell, attributable to mastery. We can get this average mastery amount from WrathCalcs (on the rotation tab, under True mean bonus) as ~83.1%. Therefore, average mastery amount will increase to 16/15*83.1% = 88.64%. This means that, since your full mastery amount fluctuates with time, on average you will get 88.64% of the maximum value displayed in your character sheet fully buffed.
As an example, say you have 100% mastery fully buffed in your character sheet. Average mastery amount is 83.1% like before, so you expect that your spells on average to deal 100%*83.1% = 83.1% additional damage. With the change, you will deal 83.1%*16/15 = 88.64% additional damage with each spell. Percent change is then (1.8864-1.831)/1.831 = ~3% increase. However, using the same analysis but with only 50% mastery, you will only see ~2% increase. Thus, again, it entirely depends on your current mastery level. I'd say mastery levels are somewhere in the middle currently (~75% fully buffed), so this looks to be roughly a 2.5% gain.
TL;DR: it's probably around a 3% increase across the board.