Exp Formula Returning Back To Normal?

There's no way she kills 50% faster than I do. If I had to guess I'd say it's about 3:2 split in terms of kill speed. (for every 3 monsters she has killed, I have killed 2).

If you can kill at a similar rate the exp change shouldn't really be a reason not to party.

For every 5 monsters, instead of 240% exp, you get 220% exp. It's still more than the 200% you'd get for your own 2 kills, even without factoring in HS and party bonus.