IMO, the 888's are terrible in a heavy rain/standing water. At the enduro, we ran (on a Pro3 car) 4/32 shaved 888's in the downpour, and if you got even a little off the wet line into the standing water, it was like driving on wet ice. I think the consensus is that tires are just to "blockey" with way to much surface area, and not enough grooving to effectively channel the water. We might have been a tad stiff in our suspension setup as well (we were carrying 29 gal of fuel), but it was mostly tire.
We found a set of 205 RA1's (the 888's were 225's) new at the ANT truck at the track, and bought a set of full depth tires and swapped them onto the car. Same driver, same conditions, 8 seconds better (memory) at PIR, no chicane.
On a damp track, I don't think the 888's are too bad.
On a dry track, I think the 888's will be quicker than the RA1's, but I also don't have the data to support this, yet. I do have a set of sticker RA1's and a set of sticker R888's - sounds like a good reason to go drive, to me!
Dan