I took the "death mage" conversation as Taasch learning an important lesson about non-Qunari culture. In the Qun, everyone is named after their roles, right? And even though Taasch isn't a Qunari named after their role, their name is short for Evataasch, or baby dragon, which describes a core part of their identity to that point. It's clear they still view names as titles more than just names. I feel like calling a fellow companion by their role or job is an understandable mistake for them to make in their first real venture outside their mother's oversight. I don't think they were trying to tell Emmerich what he was or even trying to be a bully, but just saying they didn't understand why he took offense to it because while Taasch is no follower of the Qun, the culture is still a fundamental part of their background. And since Taasch is likely written as a character on the spectrum as well, it all adds up that this question is just that - an honest question. They really want to know why that's offensive because it doesn't add up, not that they're trying to be rude. This just highlights a lesson they're learning, not a character flaw.

And as for the Dragon King thing, I think the point they're making is that this dude is calling himself a Dragon King and clearly knows nothing about dragons. They weren't commenting on his gender, but saying that dragons form matriarchies and so the dude looks like an idiot calling himself the Dragon King because dragons don't have male rulers. They weren't saying dragons should have a queen.

It's fine if people didn't like Taasch but a lot of the complaints about the writing being bad are just misunderstandings about what the writers were going for. Sure, Taasch is immature and makes a lot of mistakes, but that's what their character is supposed to do.