You make a lot of good points, but I want to boil my response down to just this; Blizzard have already shown that they are very well ‘missing the point’ in the Horde story and, with their actions to date, seemingly care not which lore they have to trample and retcon and twist to serve the current narrative. Horde players already have precious few, if any, antagonists on the other side - they are constantly given justification, sympathetic portrayal, righteousness. We have no antagonists we can just be against without being bombarded with half a dozen reasons why we might be wrong.
The Horde story (and players) cry out for clear antagonists, antagonists which Blizzard constantly sees fit to deny. Daelin is one of the few examples of a clear-cut antagonist we had, and with the renewed emphasis on him and extreme villainization of the Horde narrative, many Horde players fear that his deeds will become retroactively justified or his previously antagonistic portrayal softened and smoothed out. Not every character should make us feel conflicted about fighting them.
Please don’t take away one of the only antagonists we have left.