I think the back of the RT/10 was a situation where they'd put a ton of effort into the defining characteristics of the Viper -- the long clamshell hood, the side profile, the low & wide stance, etc -- and finishing up the rear end was an afterthought, which was corrected with the GTS.
Somewhere at home I have some drawings I found online where somebody tried to adapt the GTS rear end to an RT/10. It's more tricky than you'd expect, but the result is nice. Too bad the Gen II is dead, that's a change that I'd welcome far more than the Corolla-san's Stratamaro.
But I'll say this for the RT/10 ass -- at least it has a shape. That giant ugly Corvette rear end (thankfully we rarely see the back of a Vette) demonstrates that things could be much, much worse.