Just an outsider evaluation here:
I think what all of you are missing is the skaven POV. They got a 55 on a DC 80 check there. That means they think it was a 'failed' attempt to kill the master molder that missed the target, mostly, and not a hit on the Goblin Big Boss. So they'll go into paranoid infighting mode and their isn't even a goblin leader around to start screaming about staying on task. Magic or warp stone nonsense looks a lot alike, so they may think it was another skaven faction at work there. If the master molder doesn't get assassinated immediately he has to roll to fix his eyes.. probably rolling with a negative modifier for that. If it does succeed its now going to be trying to figure out who just tried to assassinate it. In the middle of some random slave revolt/beast jail break.
So the goblins are down a major member of their command staff an hour or so before they need to be coordinated. Also, the goblin made a DC 30 intreige roll exactly... meaning while they aren't going to infight themselves into oblivion or attack the skaven as a primary objective they are going to barely hold things together. This low as possible to succeed roll means they won't have anyone to step into the Big Boss' shoes in the short term. The skaven are actively pushed into paranoia mode while chaos and stupid happens all around them. These idiots are going to be useless for a while and going to give the dwarves time to break the gates (at least versus this faction). Also, they've got a beast break out going on so they get to have fun with those rolls to not have everything go to hell and the leadership of the goblins is in flux. So negative/reduced modifiers all around. If your really lucky any remaining higher ranking goblin will be forced to deal with that mess and not be coordinating the gate defense.
As to Hangwind's complains about opportunity costs? I think he is forgetting that most of the scouting actions are to determine IF points of interest and resources are still intact and given the same rolls it could have been a total wash of actions anyway. Long term a spell mastery triggered so long term gain on the personal side... versus slowed progress on the immediate army side. So opportunity cost 'what if's should be considered in terms of the dice rolls that actually happened. Probably not great and that 18 is for her to eat not the goblins.
So the actual major cost here is that later resources are going to be diverted away later to determine if her optional objectives are intact or not. So far she confirmed one of them is intact. One of them is gutted to the walls (and beyond) and that its currently housing a giant pile of skaven and goblins.
[ ] You've scouted this area, now...
-[ ] To the Armoury, to check if the ancient weapons remain sealed away.
-[ ] To the Temple of Grungni, to check if the holy place remains undesecrated.
-[ ] To the Chiselwards, an enormous warren of tunnels that could house any number of horrors.
-[ ] To the King's Gates, to scout the outer defences.
-[ ] To the depths of Karag Lhune, to see how far the Crooked Moon Tribe's influence reaches.
So two of 7 options of objectives (possible 4) completed and a scouting action traded for a spell mastery, enemy disruption, and destruction of an annoying anti-magic artifact. As a mage the destruction and the mastery are personal boons. Enemy disruption will lower moderifiers in the short term with possible bonus effects if the gribly factions roll poorly. That leaves five options for the remaining scouting action. Armoury and Temple are either bonuses or nothing if scouted. If they are intact you get something. If they aren't intact you only take things off the priority target list. So these two options could have been a waste of time.. or not. Toss up if scouting them was useless or not.. and MC side rolls got ugly there so...
Of the last two options Chiselwards and depths are both ways to risk getting stuck in with the boyz, alone. At least as risky as the action taken. King's Gates is best saved for last action. Best support for the invasion, with the least chance to let the goblin counter. Doomgliders may or may not have burn honestly.
So basically, Armoury and Temple results will come out in time if the invasion succeeds either way and then you can offically hind sight things to death. Chiselwards and depths are just as risky as the assassination really. Remember same rolls would be used for those options.
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I guess the biggest question is if that shoulder hit was a wound or not.