What's the reason to let the Chargers die?
- A bull that betrays you?
- Possibility of an alliance with the qunari which is irrelevant anyways because hostilities between the two of you erupt anyways?
- A arguably bad staff schematic that you can now sync with the golden nug?
Idk it just feels like there isn't a reason to not make Bull Tal Vashoth, where previously there was.
It feels like the connor/isolde/mages choice, where there is clearly a right choice. I like ambiguity.
Maybe I'm missing something that other people are seeing. Do you honestly see yourself sacrificing the chargers in future playthroughs?
In regards to the first two points, if you didn't see those two things coming from a 'sacrifice the Chargers' playthrough the moment a Qunari invasion DLC was suggested then you weren't paying attention to what was said and done in game.
If you sacrifice the Chargers, you push Bull back to the Qun, back to who he was - Hissrad. Or as Gatt so eloquently puts it - Liar. Of course he's going to betray you. Trespasser would have been a bad DLC if Bull didn't betray you under those circumstances. You've killed his friends, his family, the thing that was pulling him away from the Qun, the very thing that makes being Tal-Vashoth worth it to him. Under those circumstances, he has no reason to be loyal to you beyond the orders of the Qun.
As for the Alliance, I can't remember where it's mentioned - it may in the World of Thedas book - but Qunari treaties are not worth the paper they're written on. Why would an alliance be any different? Besides, the alliance was for the purpose of defeating Corypheus. That's been done and that is more than enough of an out for the Qun. Besides, there are some indications that the Triumvirate of the Qun doesn't intend to invade just yet, even without an alliance. There's a letter you can find from Josephine that's been sent to the Triumvirate and they do indicate that what's happening is not at their order and they intend to stop it. Whether they mean that or not isn't revealed however... but I daresay they wouldn't have been that disappointed if the Qunari woman (Sorry, can't remember her title first thing in the morning.) had succeeded in subduing the south.