Mnk/war w/ brutal, atma of apocalypse, epona's ring.
18% double attack, 18% triple attack.
Triple attack has priority over double attack (if both go to proc in the same attack round, you'll get the triple attack, but wo'nt get the double attack)
Using 100 attack rounds as an example.
Triple attack will proc 18 times.
Double attack would proc 18 times, but 18% of the time it'll be stopped by triple attack, so 18 * (.82) = an average of 14.76 DA procs.
18 TA procs at 2 extra hits per proc = 36 extra hits.
14.76 DA procs at 1 extra hit per proc = 14.76 extra hits.
100 + 36 + 14.76 = 150.76 attacks on average.
Now, let's do the same, but using 20% DA (Twilight belt).
20 extra hits, but only activates 82% of the time due to triple attack.
20 (.82) = 16.4 extra attacks. (vs 14.76 w/ 18% DA)
100 + 36 + 16.4 = 152.4 attacks on average.
152.4/150.76 = 1.09% increase in damage as compared to adding 2% DA to 0 DA and 0 TA. Essentially half the effectiveness.
The DMG+ on the kick boots themselves should give more than a 1% increase, yet alone the 5/5 set bonus on af3+2 as well as the .3% haste you're getting going from 25 to 26.
Edit: it's going to be even less than that 1% in actuality because I never accounted for kick attack damage, so the TP gain % increase and total damage % increase are going to be even less once you look at the kicks.