For me it really depends on the NPC in question. If it's a Troll Bruiser, then I don't feel bad focusing them around combat, or if it's a socialite then I don't feel bad optimizing them for social conflicts. Having said that I hope my players realize that taking on the optimized baddie in their area of expertise solo or even with a group that isn't prepared for the arena (after a first encounter) to know full well what they're getting into. Which means the players need to figure out a way to either get around the obstacle or deal with them somewhere where the players have an advantage, i.e. social combat for the troll or physical combat for the socialite, which tends to mitigate the problem.

However, for mooks, I don't stat them out all the way since they're mostly just there as scene dressing.

This would seem to me to be a case where Thaumaturgy would work well for the application in mind over Evocation. It would require more footwork and would certainly make for more interesting game play as the player hunts down pieces for the ritual which could be anything from ghost dust to a bone from the corpse of the ghost (assuming that's available, or said spirit had a human body at some point).

...and we do have a new rule for his armour we're doing it realistically, "Prolonged fire spells will end up with your flesh melting to the armour, lightning spells will hit you over others..."

 While I can understand the logical reasoning for lightning to hit him over others, in general magic doesn't have to follow the rules. Personally I'd make it easier for spells with an electrical component to hit him due to wearing a very excellent conductor, but not have them automatically drawn to him. That way the armor still has a penalty but the player can't stand by the rest of the group and 'protect' them from a lightning wielding fiend just by standing by them. Granted that's not so great for him but it is a big advantage for the rest of the group. That's just my take, ymmv and it is your table.

That would really depend on your interpretation of 'angel'. Are you thinking about a specific choir of angel ( http://en.wikipedia.org/wiki/Christian_angelic_hierarchy ) or are we talking just generic angel? The answer to that will have a big effect on what powers you're looking at.

I'll have to dig into my Arthurian stuff for anything useful, but the suggestion of having her be affiliated with a seperate court is decent.

Oneiromancy - Dreams/Illusions, at least under Channeling. Under ritual it would be a subset of Divination.

I'll try.

The interpretation bit is completely understandable since that's personal preference.

What I was trying to say about the effect of the stunt is that I couldn't find any that worked exactly like that. I've seen straight +2 stunts and stunts that are +1 on a broad subject with an additional +1 to a narrower focus for a total of +2. The only things I've seen that become less effective are armor or attacks vs specific armor. That had me a bit puzzled on why you worded the stunt the way you have.

I can understand that, like I said it just struck me as odd and even looking at the rules and examples last night I couldn't seem to make the wording you've used for that fit for effect, though I may not have done as much looking as I could have.