Other than oasis

[Splorf22]

Guktop is one of my favorite dungeons (it has an insane xp mod) but I think 15 is just a touch too low, unless you can find a partner to help you do the spiders. 17 would probably be the minimum if you want to do the Scryer or the Undead zoneline, but after that it will take you all the way to 30 if you want.

Kurns is fantastic at 15 (up to about 19 if I remember correctly) but its a long way from Oggok and I'm not sure if there are any warrrior gms in the outpost.

Unrest is also fantastic at 15 (doing yard trash), and you can move inside starting at maybe 17-18 or so, but again there isn't much in the way of support for evil characters on Faydwer.

I suppose all of this depends on your level of twinkage, but in my experience the tanks and enchanters suffer more from being underleveled than dps/healers.