Weapon damage is either Kinetic or Energy. Pretty sure it applies to both.
As to Elemental and Internal, I'm not sure. It makes sense for it not to apply at all to Internal and I can buy that.
Edit: I'll find someone in guild to duel to fiddle with this a bit, see what I come up with.
Don't get me wrong, I'm not a fan of Shields either, I think it's a clunky mechanic that requires a LOT of investment for little returns. I'm just saying that you probably have what it does and does not mitigate incorrect.
We tested last week in duels and Shield Chance doesn't work vs Kinetic nor Elemental:
I was surprised by the results because it makes Shield Chance a weak mechanic in PVP.
Let us know the results of your testing.