You have 3 mandatory skills in all situations:

1. Convalescence
2. Internal Release
3. Provoke

So, you've got 2 other spaces to fill. The 3 best choices are Second Wind, Awareness, and Flash. In 4mans and A2/A2S, you want Flash + Awareness. In places you don't need Flash (Ravana, A1/A1S, A3/A3S, and A4/A4S) you take SW + Awareness.

Basically, there's no reason not to take Awareness. Flash can be optional in 4mans/A2/A2S, but it's a good safety net to have just in case. Second Wind is half an Equilibrium that you can use in Deliverance, which is really good for a lot of things. Mantra is also an option, but usually not that great. Everything else is garbage.