It's no good, Ronin83, people whose legs conform to the average trouser don't understand the problem.
I regularly grit my teeth in outdoor shops when contemplating the inches of trouser leg sweeping the floor. And it's no good saying cut the bottoms off the legs, as walking trousers usually have some kind of shaping at the knees, and so even if you altered the legs to the right length the knees are in the wrong place.
There do seem to be trends in this, a few years ago, most walking trousers could be cinched in at the ankle, and I remember being told that it was precisely to accommodate different leg lengths, but it seems less common now.
I tend to wear Paramo trousers, they don't need overtrousers. I have both cascada and velez, and both have ankle adjustment. They aren't cheap though. I justify them to myself on the grounds that they are walking trousers and overtrousers in one, and you get 50 quid back on the empties.