In regards to dipping:
Oracle (Lame) lets a Barbarian end Rage and restart it without being fatigued.
Meaning 1/rage powers become 1/rd: this opens up options.
Unfortunately, while that is a great combo, dipping into oracle doesn't work for the Barbarian as you need to get to lvl 5 in Oracle to get this benefit.
So while you could make a Oracle/Barbarian build that works great around this, or even an Oracle that dips into Barbarian for two levels... it doesn't really work dipping Oracle.
Sean