Streamlight does list output in terms of lumens on their website...
That aside, I totally agree with what you said.
It's next to impossible to try and compare the output from lights from different companies.
In my case, I tend to rely a lot on data from quickbeam's site when numerical figure are needed.
He doesn't have every single light available on the market,
but what I do when he doesn't have the light is to just look at the numbers provided for another light by the same maker and extrapolate from there.
Of course a good idea would be to just send him every light in existence and slave-driver him into doing charts for all of them.
But the only 2 problems would be finding people to supply the lights and getting quickbeam to agree to being our resident beast of burden!