So the majority of the Shattered Sanctum can be handled in pieces.
1. Priestess Gut can be isolated and killed
2. Minthara can be killed with her little team
3. Halsin can be freed and all those goblins killed without alerting as long as the kids don't escape.
4. The torturers can be killed without alerting.
5. The Goblins near the Mugubliyet prisoner can be killed without alerting.
That just leaves Dror Razlin as the big fight that turns all Goblins hostile. You have a lot of resources to help you get through this fight and ways to approach it. Its a long fight but not a particularly difficult one.
1. Coal filled braziers sitting over the main throne area that can be shot down (in turn based mode/or multiplayer you can do more than one)
2. Wooden Beams over the battlefield where you can place a sniper/bomb thrower.
3. Lots of pillars to hide behind and take shots at people to force enemies to come to you without you being exposed.
4. Finally, the actual enemies are quite weak. Only Dror Razlin and a couple of bosses have any real health.
If you handle the battle carefully and draw the goblins back into the room without chasing them you can rest before having to Mop up the remaining Goblins.
An alternate way to handle this is to Get Minthara and her troops to attack the Druid grove (then betray her and kill them all with help from the grove) and that will deplete a lot of the goblins in the shattered sanctum, making it easier to kill everyone later.
