Gnome(hp trains) for any cabal that can be neutral. Human(no vulns) for other cabals.

As nexus you can get some sweet boosts through the bond.
As scion you will have a ton of hp and a nightwalker to help you do stuff while solo.
As fortress you will likely be Acolyte. No awesome powers for you.
As trib you can sit in towns and only fight when your enemy is wanted or they attack you and you make them wanted. Guards to help out.
As outlander you only fight when you want to. If you die then as a def/def shifter I dont really know what to tell you.
As empire you gotta be nuts. Why go there as a shifter?
As scarab...well. You wont die defending your cabal, thats for sure.

Avoid necros and you should not really die unless surprised by someone. A necro can ruin your day with forget. But can you survive the boredom of not being able to do anything on your own? Most fun of the cabal choices would likely be scion.