Actually what you did was increase the downstop but reduce the droop. But you used one of the things that we usually do to reduce chassis roll.
The biggest contribution to the solution was most probably the reduction in front droop as this makes the inside front wheel unload earlier in the corners reducing the dive onto the front outside wheel which lifts the inside rear wheel of the ground. The rear droop helped in that it reduces the amount of weight transferred to the front when going off power (or braking) to enter the corner. As a result more weight is kept on the rear wheels keeping them on the ground.
Other options suggested are also good to try. Like TigeRyan suggested it can help a lot to run harder springs and damping on the side of the car opposite to the one where the wheel is lifting. In this case you would need to run harder springs at the front as this reduces front chassis roll similar to the decreased front droop (= more downstop). The difference between the two is that generally harder springs will also reduce front traction both on and off power while the increased front droop will decrease front traction into the corner but increase front traction exiting the corner (less weight transfer to the rear!).
As to Sam's statement that maybe more rear droop is actually needed, this is a pretty good theory as this can actually work out better in some cases. The trick here is that the inside rear wheel will unload sooner, so while more weight stays at the rear off power, you also take away some rear-end grip throughout the corner. The question is whether the increased weight will increase grip sufficiently to offset the lost grip due to the inside rear wheel unloading sooner. Nothing is ever easy is it?
