Your response is not terribly unusual, and was the motivation behind a post by theferrett (I'm terrible with the LJ user tag, but remember the double-t if you go looking... poor theferret, single t, gets a lot of unexpected traffic from folks who forget), which I believe led to the poll that in turn led to this post.

In the absence of a better term, and as yet none seem to be popping up, I'm not sure how to respond to this sentiment.

I'm also not sure in what context you mean by "in context", because I think it's been pretty clear that when cis* is used in sentences as the clear opposite of trans*, then that clearly shows its meaning.

I'll add to this by noting that the terms transsexual/transgender meant nothing to me the first time I encountered them, because I'd never heard them before. That the prefix 'trans' suggests a crossing of some sort was not enough. I don't see them as failing as words as a result.