Sneaking is op because you can start a battle with a sneak attack from Astarion and then the combat tracker is just Astarion and the enemies that saw him, or maybe only the little pillar of light that shows up.
Once Astarion gets locked into the combat tracker you can still maneuver everyone else around the enemies sight lines and get a few more alpha strikes in outside of the combat tracker. My paladin -- in full plate -- can walk right up to an enemy that's frozen in the combat tracker as long as he doesn't walk into the sight cone.
I beat dror, m, and gut in the goblin camp all without any of them taking any turns because I was able to alpha strike them into the dirt by just starting combat with the whole party sneaking, and then walking them right up outside of the combat tracker.
Is there a party that can really exploit this? Ranger, wolf barb, shadowharts +10 party sneak, and an assassin rogue? Just alpha strike everything.
I actually cheesed it the other way--my tired and battered party was trying to exit the goblin camp without fighting the main force in the courtyard (at this point, I didn't know I could fast travel when not near a portal, and wanted to play it out for RP reasons anyway).
So I sent my thief out first, and he disengage/sprinted through the entire camp, drawing all the attention. Once everyone was drawn away, I let combat sit there "paused" while the other three party members waltzed out the front door and off to safety. Then my thief outran everyone.
Personally, I wish Larian would have given the option to lock the entire map into turn-based mode when combat begins anywhere, but I know it's not everyone's cup of tea (especially with multi-player). Just my preference.