I don't have Invisibility yet because all my air spell slots are occupied. I am thinking about getting Aerothurge 3 just so I can pick up Invisibility and Tornado, though.
The issue with the Scoundrel skills (and Tactical Retreat) is that this build does not have enough Dex to guarantee success when using them.
Yeah, there's not a lot of Talent points that look appealing. Maybe I could get "What a Rush", but I think at least one will be traded in for 2 attribute points.