Hmm. On the one hand, Amanda's demise was senseless in a way that transcended the senselessness of Tasha Yar's demise in Skin of Evil.
(At least in that case, there was a point to the pointlessness.)
But on the other hand, we don't know that she's dead. She may be wiped from ever having existed in the multiverse or in the Q Continuum, but all we really know is that she's in the Omega Continuum. Which is also all we know about q and Eden, for that matter.
In addition to the B5 parallel I already mentioned (and will Janeway suddenly either drop dead or vanish without a trace in precisely 20 years?), I also see parallels with the very first Pocket ST novel (not counting the novelization of TMP), The Entropy Effect.
In both novels, changes to history are involved, and in both novels, they're linked to accelerated heat-death of the universe. And I also find myself thinking of The Wounded Sky.