Feeding does not increase your rating. Your rating increases upon leveling up and is rather dependant on your Pedigree (starting rating).
Before feeding:
After feeding:
Same rating of 179 as you can see. So I was indeed racing with a handicap of -14 training sessions (and still getting 1st place) which, at P9 and 3 stars translates to 14 stat points when fed with Level 3 veggies. If I had the MGP to spend on level 3 feeds I would have an extra 196 in stats, totally blowing away the competition. So should a P1 ever meet up with a P9 in the same rating (say at R120) and both train their Chocos with Level 3 feed, the P1 will only get a +3 stat boost while the P9 gets a +14 stat boost (3-star stat).
The difference is huge and when a Choco levels up 3-4 times within the same bracket, the difference is drastic. P1: 3levels x 3 = 9 stat , P9: 3levels x 14 = 42 stat.
How then should SE balance the AI? I do agree with you on the feed cost though. It is so prohibitively costly that it discourages people from even buying them until that perfect bird comes along, and that's where the complaints are coming from isn't it? Low pedigree + cheap feeds mean that your stats look something like:
Rank 40
Speed: 150/300
Endurance: 150/300
Racing against high bracket NPCs who are catered towards higher pedigree racing:
Speed: 300/400
Endurance: 300/400
Wherein lies the problem. In order to be competitive you'll have to constantly breed your Chocobo to a high Pedigree. It's a big time sink and a big MGP sink. Stats on Covers are randomized, good fledgelings are miracles. The prohibitive cost of high level feeds/covers + RNG involved in producing a reliable Chocobo takes way more time than Triple Triad. Racers also want some MGP to buy those shiny cosmetic stuff right? Yet they have no extras, no leftover MGP to spend.
The only time when there's decent and reliable MGP returns from Chocobo racing comes at the end R300. But by then players are bled dry of MGP, sunk hours and hours into a minigame and so sick of the whole racing system. Yet SE knows they can't make it any easier because like Triple Triad, once you unlock those 60 cards (P9 Chocobo), it's yours for the years and years to come.