As people have already mentioned for pushing challenging content food is definitely worth it. Assuming you can cap determination on HQ risotto (at least 340 det) using stat-weighted adjustment, it's like adding another 7.5 strength! That would be the equivalent to jumping 30 ilvls on an accessory piece... Think darklight to weathered soldiery. The stat-weighted adjustments for buttons is similar albeit a little less. Do you still think it would only increase your dps from 370 to 371?
I challenge you to go to a striking dummy and do your rotation for 3 mins. Once with out food and once with food. If it isn't at least 5% higher with food, I'll send you the cost of the food.