Good point, and Brandon does tackle the issues. But at the end of the day a feudal Alethkar is going to be immoral by modern standards, and it's unlikely that even a decent person like Dalinar would question the system. It's just not in their cultural consciousness. Does that make him "deeply flawed"? Perhaps, but he wouldn't even think of it like that. What him and Gavilar, as well as every highlord, do and did in their any of their wars, would be considered a war crime today, but all he and his soldiers regret is the Rift, because that was, even by their standards, beyond the pale.