Much of it does sound pretty similar but I wouldn't include Tenhi there. Obviously there are similarities, but I think Tenhi offer something a bit different to most of the dark folk music I've heard. And even their own 2 full lengths are actually pretty different themselves.I like the genre, but Empyrium, Tenhi, "Kveldssanger", Forseti and such all sound the fucking same to me.
Of the Wand and the Moon are pretty good. Their latest "Lucifer" has it's moments, but I think there are better bands out there.
Try:
Hagalaz' Runedance
Foresti (a must)
Stille Volk (pretty weird, incorporate lots of different styles)
Sonne Hagal
Hekate
I also really want to hear that Uaral band, will do soon.
edit: these are dark folk bands, not folk metal bands, which I probably should have mentioned.