Agreed. I would not put $750 into a D30 unless it was for an ARB. Gears and lockers are about the only upgrades I would do on a D30. I am running 35's on mine with stock brakes and have no issues. I did notice a difference in braking when I put an 8.8 in the rear with discs. I don't think that you will see that much of a difference to make it worth it.
When mine used to be a DD, the biggest braking problem I had was in the snow. My front brakes would lock up while my rears would barely grab, making me slide forever. I took out the proportioning valve which helped, and then the discs in the rear helped too. You will still slide a bit in the snow, but I think that is because Jeeps are just so light, especially when you put a bigger footprint on them.