It obviously didn't go the way he wanted it to but I think the show would be pretty boring if he was basically a super hero and always made the right decision.
How would you have gone about trying to kill thousands of zombies trapped in a quarry? Anything I can think of seems pretty impractical. They wouldn't be able to walk in there and take that many of them out quietly. If they used guns it would have taken thousands of bullets, probably more bullets than they have, to kill all of them. On top of that it would make an incredible amount of noise that would only draw more herds of zombies or other gangs
Maybe a fire like the one Daryl made in the lake would have worked but it would have to be massive. It would have been pretty much impossible to make a fire big enough without the fuel tanker though, and again they didn't have this until after Rick's plan went to hell. Even if they did there are problems that come with making a fire that big intentionally too. If you do it at night it would be a source of light and noise to draw more herds of walkers in. If you do it during the day it would be a massive smoke signal for every gang within striking distance.