Not villanizing outsourcing. It's commonplace, we know, but ND is particularly known for its in-house "no producers" development which has largely led to its success. I don't know about the cost of this outsourcing on TLOU2. Who knows, maybe it is a new, better solution financially and stability-wise than before... but the amount of departures and turnover just tells another story IMO.
I've just learned from other franchises (mainly BioWare) that when the management squeezes too hard the talent runs out, and then if they keep doing it, outsourcing isn't going to be enough. TLOU2 impressed me with how good it was after how much I thought people of talent had left, so we'll just have to wait and see if ND even keeps making these kinds of games for 5 more years.