Making a deal with the evil, twisted enemy is also another red flag, no matter how you look though, we have plenty of example of those things not going the right way, who could possible think of something good coming out of it?
And i would not excuse her just because we are able to flip out.
Point is, she sure was not an entire villain in the horde eyes in Legion, but the expansion raised enough red flags to set up her to be a villain in BfA, the problem with BfA all together was badwriting and how they escalated too quickly, it was coincidentally, the same problem with Garrosh, turn then into hitler and call a day.