All of my alts are mining and herbalism. Herbalism pays off pretty good in the high levels: Dreamfoil, plaguebloom, golden sansam, icecap, black lotus... so many herbs that sell very well. Mining is such a pain, even with L60 alts I haven't managed to get very deep into mining thorium yet. Arcane crystals (which rarely drop out of rich thorium veins) are extremely rare and not something you can consistently farm for money.
Summary: Herbalism good. Mining okay.
As for skinning, my main is a skinner/leatherworker. Nothing leather really seems to be particularly valuable. Devilsaur stuff sells "ok" but not great.
I do agree that fishing can be quite profitable. Stonescale eel sells very well and will always be in high demand for the production of flasks (and even moreso in 1.11 as it is used in a new Argent Dawn turnin). Also, the dedicated fisher will do well in some zones hunting various fish in 1.11: There are added pools to fish in that guarantee catching more valauble fish. For example, there are schools of stonescale eel in Tanaris in 1.11. Very handy if you're running around trying to make a quick buck.