Against anything fodder, while using food, attack is going to be capped. Mithra THF/WAR with Mandau main and using Atheling has 570 base attack. Toss on red curry and it's 711. All this math tells me though is that AF2+2 feet aren't optimal against anything but fodder. The 3% TA pales in comparison to 3% Haste, for many reasons. Athos would probably be better in that slot against anything with higher defense.
Well, obviously if you're capping attack then you will want to start changing out gear, since you're not getting any benefit from the attack. I didn't think that needed stating.
I'm not sure how you're reaching the conclusion that AF2+2 feet aren't optimal on higher tier targets, since the point you refute only has to do with AF3+2 hands. Against lower level targets, if you're capping attack you might as well swap AF3+2 hands to Nomkahpa. Against higher level targets, it's already presented that the AF3+2 hands will likely win even if you're not capping haste.
As for 3% TA vs 3% haste on the feet:
Value of 3% TA, is an increase in average hits per hand of 2 * 0.03 = 0.06. The relative value of that depends on total average hits per hand (and thus dependant on existing TA and DA).
Suppose we assume /war, Brutal, Atheling, Twilight and Epona's for DA: 23%
And we assume trait, merits, Epona's, AF3+2 head and Triplus for TA: 19%
Average number of swings per hand would be 1 + 2 * (0.19) + 1 * (0.23 * (1 - 0.19)) = 1.5663
Relative increase in number of hits (not counting +TA damage) would be (1.5663+0.06) / 1.5663 = 1.0383, or +3.83%
Triplus (estimated as +3%) and Relic+2 (tested as +2%) modify the effective damage done, though.
At 19% TA rate with Triplus, 0.57 hits out of 1.5663 will be TAs, and gain an additional 0.0171 effective hits of damage (melee damage only), for a total of 1.5834.
At 22% TA rate with Triplus + AF2+2, 0.66 hits out of 1.6263 will be TAs, and gain an additional 0.033 effective hits of damgae (melee only), for a total of 1.6593.
Melee damage thus increases by 1.6593 / 1.5834 = +4.79%
Since melee damage is only about 1/3 of all damage, I'll use 1/3 of the difference between those two values later on. First, comparison using the +TA rate only.
Total haste with AF3+2 head/body/legs + Twilight: 234/1024
Gain from any haste on feet: 256 - 234 = 22/1024, 2.15%
Value of a given amount of additional haste is (1 - current haste) / ((1 - current haste) - additional haste)
h == 1 - current haste
So at what amount of current haste is 2.15% additional haste worth at least 3.83% damage?
h / (h - 0.0215) = 1 + 0.0383
h = (h - 0.0215) * (1 + 0.0383)
h = h + 0.0383h - 0.0215 - 0.00082345
0.0383h = 0.0215 + 0.00082345
0.0383h = 0.0215 + 0.00082345
h = 0.02232345 / 0.0383
h = 0.583
So at haste values of over 41.7%, the haste feet have a chance to start outdoing the AF2+2 feet. However that doesn't account for the +TA damage.
Now, the additional melee damage. 4.79 - 3.83 = 0.96 / 3 = 0.32%
Add that to the 3.83% gained from just +TA and the total is 4.15%
Run through the eqivalency math again:
h / (h - 0.0215) = 1 + 0.0415
h = (h - 0.0215) * (1 + 0.0415)
h = h + 0.0415h - 0.0215 - 0.00089225
0.0415h = 0.0215 + 0.00089225
0.0415h = 0.0215 + 0.00089225
h = 0.02239225 / 0.0415
h = 0.540
So at haste values of at least 46% haste shoes start doing better than the AF2+2 feet.
Note that 46% is when current haste is using the 23% gear haste value, so it is an additional 23% haste on top of gear haste. That requires the Haste spell plus either a dnc main's Haste Samba, or Marches, for haste shoes to be the better option.
In the case that the haste shoes offer additional benefits aside from the haste itself (eg: Savateur's Gaiters, Setanta's Ledelsens, dex that affects crit rate, etc), you can probably assume that they're worth using if you're at least getting Hasted.