Nice dig… 
… But not correct.
The constraint on my levelling of troops and heroes is seldom food. The constraint on these is the rate at which I can produce hero fodder and/or find troops. These are pretty much constrained by the game timers - hero fodder takes time to produce, and troop acquisition is a product of farming the map and/or random tokens. Map farming is constrained by the world energy timer.
So while waiting for the timer I’m producing enough food so that when the resources to train my heroes and troops become available (the hero fodder and the fresh troops) then I have more than enough food to meet the training requirements.
Oh… and the other constraint is higher level ascension items… and THAT is why I ‘farm’ hero wanted missions - to increase the rate at which I turn over missions to thereby increase the chance of a rare wanted mission arriving, which has a reasonable chance of providing the ascension items I’m looking for.
Food becomes an occasional constraint, generally after spending a whole bunch on research or an ascension… but it resolves itself naturally as you need to wait for the natural game energy and training timers to expire. The other time it’s a constraint is after a tough event or quest in which you’ve need to consume large numbers of potions to succeed - crafting new ones to get stocks back up is expensive. But that’s only an ocassional and temporary constraint.
Bottom line is: I don’t raid for resources, and I certainly don’t do it for fun. (I find the raid mechanic irritating). I raid for Hero Wanted Missions.