I generally concur with your ranking of the segments here, particularly in regards to "House of Whacks" - whereas I harbour a mild disdain for the nonchalance and disinterest with which "Hex and the City" blows through the most potentially compelling aspects of its concept in favour of a malaise cartoon in which the writers almost appear to assume that showcasing the barest skeleton of the concept (yes, Bart has an elongated neck, but how does this reflect or accentuate any aspects of his characters beyond the obvious one-trick twist on the ye olde Homer strangulation gag) is substitution for legitimate narrative and atmospheric realization (essentially marginalizing the plot into a gimmick as opposed to the perversely unique distortions of OFF offered by the Halloween spectacles of old), alongside the sheer sloth of "Wiz Kids" (in which the focal 'parody' in question scarcely resembles or subverts the source material to the extent of effectively masquerading as 'Harry Potter' via only the flimsiest cosmetic pretenses), "Whacks" is arguably the sole segment of XII to actively pursue a focal concept and approach resembling (to some extent) the most effective 1990s segments: in essence, the concept of a silkily coercive HAL ersatz is actually implemented into an aspect of the show's normalized template (in this case, the garishly-coloured yet persistently stable mundanity of the Simpson household and the extent to which Marge is anchored to it) in a unique and (if inconsistently-written) eerie manner, resultantly enabling the segment to collide its abnormal elements with Marge's established role to yield a more atmospheric and investing disruption of the show's typical narrative and conceptual rhythms than merely lackadaisically inserting the equivalent of a Harry Potter logo onto the barest pretense of the show's typical comic routines.
The THoH 'approach', at least in its most optimal and effective (pre-Scully) format, tends to reach its greatest heights through presenting unearthly or satirically eerie disruptions of a specific idiom governing the show's structure (with the bristling oddness of the juxtaposition often catalyzing that unique perturbing tone held by the likes of "Time and Punishment" and "Bad Dream House") and tonality before subsequently accentuating the perversity and consequences of its presence and impacts upon the characters in such a way to amplify and malleate the resultant distortion in the manner of an escalating macabre and anarchic nightmare - in essence, the greatest THoHs are essentially creatures of atmosphere and concept more than (necessarily) raw plotting, deliberately and pragmatically tainting the typical flippant discord of the show's setting and comedic tonality to present a form of unique Gothic caricature of the unnerving aspects underlying the mundanity of both the Simpson universe and the viewer's (thereby displaying the show's once-towering ability to mirror and scrutinize social reality, albeit in a different form from the typical 'classic' OFF episode), and, while "House of Whacks" falls short of these heights owing to its more glaring narrative faults (chiefly a mild overreliance on scatological/sexual gags and Homer's role eclipsing that of Marge during the climax to the effect of weakening her stakes in the narrative), it's certainly closer to this template than the dead air surrounding its runtime.
On a related note, looking forward to your critique of the Jean era, particularly the much-maligned likes of "Brawl in the Family", otherwise an ominous trend-setter to an interminable run.