Hey all, update on this.
1.0.8 will now have XP shrines multiplicative, and MF/GF from Fortune shrines will exceed the 300% cap.
As an aside, we realize XP shrines aren't useful to players who are P100. I want to acknowledge the issue but you won't see any changes to address this in 1.0.8. We also realize that the MF/GF 25% from Fortune Shrines is small relative to the 300% you already have when you are P100. Again, something we could look to improve in the future, but not in 1.0.8. For 1.0.8 we're only going with the change to exceed the cap.