The path I've followed, so far:
- Gained a few levels, then finished the Crypt
- Went straight to Ishad N'ha, fought around for some more levels in the midlands, then finished the Temple
- Made my characters really strong (Which took about 7 days of just fighting monsters in the midlands), then went and completed the Boogre Prison
This ended up making the Boogre Prison very easy to complete. I've still got to go talk to Grunaxe's ghost, I went through it so fast that I forgot to look for him!