Guild dungeons aside, there's no real alternative to Skellington.
I tried Geffenia, its hard as hell and the drops are nowhere as good.
The alternatives you mention are just wishful thinking for when you cant bear to look at another Dullahan without throwing up. But when you need to make both money and xp fast, you'll head back to Skellington, no doubt about it.
Try Niffing with a poly clip to break up the monotony. I actually got a Sohee card recently polying in Niff, that was awesome.
