Our trip was early November, and also the Wine and Dine 1/2 Marathon weekend (though we did not experienced issues getting FPs during the TOT 10 miler in 2013..FP+ was still in testing then, though). We did not find the parks to be excessively crowded. Touring Plans has our first MK day as an observed 3 (predicted 4), DHS was observed at a 6 (predicted 7), and our 2nd MK day as a 6 (predicted as 5).
On 1st MK day (crowd level 3), when we went to the kiosks all that was left was Dumbo, it's a small world and something else (can't remember..Philhamagic maybe?), only 1 time option available (first
MVMCP of the year that night). At DHS I can't remember what was available, but I know that Star Tours, RNRC, TOT, TSMM, F! were not. We grabbed a FP for Indy just because. We were shocked that ST wasn't available at 3:15pm. We have never had issues getting ST FPs, at any time of day. We didn't bother with FP+ on our 2nd MK day, as the A&E FP+ I had didn't open til 4:40, and it was another MVMCP night. Based on our experience on MK day 1 looking for a 4th before that time, we weren't hopeful so we just headed to Epcot for the last night of F&W.
If we'd been able to use 8 FP+ at MK and 6 or 7 at DHS like you did, and as we have been able to do on previous trips, we'd likely have a different opinion of FP+. Just wasn't our experience. I'm not claiming it will be the OP's experience either...honestly hopefully it won't be

Just offering some advice that during party season having your prebooked FP+ end earlier in the day may help you get more at the kiosk.