1) If you are working on heroic progression (of the normal, "our guild finally got that boss down on heroic" sort, or of the "we're world/realm first" sort) at all, you clearly aren't terrible.
2) If you are working on heroic progression, your guild has probably wiped enough that battle-rezzes are important considerations. Paragon wiped 500+ times on heroic Ragnaros (
source) before they got the kill. It's fairly safe to say that most current-content heroic progression bosses will take a few dozen wipes to down, at least.
3) Being generous, say a relative +25 Int = a relative +100 dps. On a 10-minute fight, that's 60,000 extra damage. A single "lucky" (that is: one more than the expected long-term average) overload proc on a lava burst will eclipse that. Failing to get as many lava burst overloads as expected (the long-term average) will have more effect than choosing to eat a lesser food. RNG has a greater impact on DPS than the difference between +275 and +300 food. On shorter fights, the effect is more pronounced -- there's less time for RNG to smooth out, so a very lucky or very unlucky pull is more likely to occur.
At level 90, 300 Int gives about 0.16% crit. If you had 300 spellpower and ~100 crit (just a bit under), you'd have the same gain as 300 Int.
Comparing orcs to pandas, though, you have to consider when Blood Fury is being used -- it's a lot stronger than the theoretical average of 282 sp when it's up while Ascendance is (sitting on it for every Ascendance might be worth more than using it on CD). Also, there's orc's +2% pet damage, which applies to elementals (but not searing or magma totems).
In sum: RNG has a bigger effect than the difference between reasonable food and the best food. Provided that you are making use of them, the difference between racials is small -- generally smaller than RNG and human error account for.