Yeah, you measure it :)
Get a steel ruler, with half mil markings and measure the distance from the fret to strings from 12th up. If the action lowers as you go up the frets (it should stay much the same, or *increase*(doh!) slightly) the neck is angled back too much. You may have to guess a bit between the half mil markers. Human vision has a resolution a bit better than 1/10th of a mil though, so you should be fine :)
And get something with a hard straight edge, preferably metallic, so it'll make a nice clear clacking sound, about 3 inches long and go up the frets, resting it on a few at a time, shifting it by one at a time and rocking it back and forth. If there are high frets, when they're in the centre of the improv-fret-rocker, the fret rocker will rock (and make a noise if its metal).
If youre really unlucky it could be both frets and neck angle, but with the actions you've stated the frets would have to be visibly very worn, and to different degrees, for it to be just that. On reflection, from what you've said, I cant possibly know for sure, I suspect the neck, so have a look at it, and I'll be delighted to be proved wrong! (its a pain if it is, for you and whatever poor tech you take it to).