Improvement Ideas for Guardian Build?

I’m trying to figure out how to skill a Gundian, but not for the usual shrapnel approach (which I strongly dislike) but for running with Surgecasters/Stormcallers/Stormcasters and maybe some other guns as a secondary set.

I currently plan on running a build something like this.

Now for the questions:

  1. Do skill retrainers refund the initial forced skillpoint (e.g. in Shield Bash for Guardians)?
  2. Shield of Faith looks too weak to use as a 1-point panic button, or am I overlooking something? Great Defender combined with defensive injectors/shield capacitors looks way more effective as a panic button.
  3. Is Grand Aura worth taking for Gundians? Anything close to me is hopefully bound to be shocked and busy dying anyway…
  4. I’m trying to look for ways to boost damage beyond Anchor, and to use skills besides Anchor and firing the guns. Does Prayer of Retribution make use of shield penetration on armor? If so, does it have enough elemental attack strength to at least semi-reliably phase mobs in Nightmare, Stonehenge and the Abyss?
  5. Are there any other ways to improve on damage output and/or survivability?

I can only answer point 1 and that is: no, a retrainer doesn’t give you that skill point.

Thanks! I was kind of expecting that this was the case, but it’s good to have confirmation.