I think the Crystalvein Mine in Stranglethorn Vale would make a decent grinding spot for level 40-45 or so.
You have to go there and kill Ironjaw Basilisks (43-44) to get crystals for a quest:  The Singing Crystals
It's a nice spot because there's lots of Basilisks and nobody goes there because there's only one quest with a drop rate is so high that people complete the quest just inside the entrance of the mine.
There's several mineral vein spawns (I saw mithril and iron) in the cave as well as a few just outside, several chest spawns, and lots of leather from the basilisks if you're a skinner. There's also some water, so you might be able to fish. I never tried though.
I think that the rare elite spawn, Scale Belly
, can also be found inside or outside the mine.
I think it's probably one of the most secluded grinding spots in STV, which is a plus if you're on a PvP server since we all know what a warzone STV can be.