Timing is something to consider here...
B417
If you aim both attacks at a single opponent, he defends at -1 against them, as his attention is divided!
B370's explanation of Rapid Strike, OTOH, does not give the "divided attention" penalty. Nor would there be that penalty if using Extra Attack, whose baseline use (sans Multi-Strike enhancement added in powers) doesn't even allow the reuse of a limb, making it resemble DWA more than RS.
Nor does AOA double give that penalty. DWA seems unique in giving the -1 to defenses due to divided attention. That's got to be the TIMING, right?
DWA very much seems to resemble P166 "overwhelm" except only half as good, probably because 2 attackers divide your attention more than 1 attacker with 2 weapons. 1 weapon is sort of 'waiting' for the other.
DWA seems to have option to trade "can attack two foes" for -1 to defenses. Presumably of equal value. More like two techniques in one, really, except you can buy it up together. Not sure if this means RS can only target 1 foe?
The -3 to attack giving -2 to defend is a better deal than what you usually get for Deceptive Attack. Especially if using +1 for same source (-2 gives -2) or +2 for same power (-1 gives -2) since it's "easier to coordinate related powers" (sadly it seems normal combat can't benefit from that)
Unlike Deceptive Attack you can also buy this as a technique, which makes it compete more with something like Counterattack.
Rapid Strike requires "a ready weapon" for the 2nd attack, and may be assumed to imply sequential attacks with a single weapon. That's probably why there's no 'divided attention', because by the time the 2nd half begins, the 1st half is resolved.
Yet there's not actually anything preventing you from using 2 different weapons for a Rapid Strike... and when you do so, there's still -6 to hit.
Rapid Strike of course has rules which only apply to it and not DWA (B93: half for TBAM, B357: half penalty for 1 FP via Flurry of Blows) further complicating things...
Given that Rapid Strike can represent "I thrust-impale with my sword, then pull my sword back, and thrust-impale with it a second time" I see no conceptual problem with "I don't need to divide my weight between the thrusts" like I would with simultaneously (split attention) thrusting 2 swords forward at the same time.