I do agree in many ways, though I think that the very best villains are always corrupted good guys- even in most Christian religions, Satan is a fallen angel, once Lucifer, son of the morning, one of the greatest angels in heaven.

Sargeras is essentially Blizzard's Satan.

Satan didn't, however, have the excuse of seeing undeniable evil- vicious, greedy, conniving, selfish, arrogant, pain-loving Nathrezim and Old Gods as an excuse for "Going Mad,"- and I always think Blizzard means something different when their Lore-weavers say this in most contexts.

That is to say, when Gul'dan gets so power-hungry that he trusts to anything at all for help at getting the power he desires (and it gets him killed), he has, in this respect, gone mad. What sane being would willingly accept the prices he paid, with little to no assurance of the object being paid for delivered? No sane being, that's who. Only a madman- twisted with visions of himself commanding forces beyond mortal ken- would do the things Gul'dan did. He had "Gone Mad"(tm) Blizzard style.

I'd expand that by saying, those of you very familiar with LotR, Saruman also "[went] mad"(tm) believing what he saw in his Seeing-stone, doing what he did to try and topple Sauron and take his place.

Malygos, on the other hand, didn't "[go] mad"(tm). He just went mad. Losing his best friend Neltharion, much of the Dragonflight he commanded, pining away for ages, and waking up from his misery-induced slumber to find his prime directive so universally reviled, he went mad, felt he knew just what needed to be done, and proceeded to attempt it. Malygos experienced psychosis in his way- that is, once again, he went mad, he did not "[go] mad"(tm) Blizzard style. We had to put him out of his (and our!) misery, in much the same way as one has to restrain a person in charge of nuclear missile who is experiencing hallucinations that [insert other country here] is currently launching nuclear missiles at his own country.

Or so I see it. Could be wrong, but all I can do is call 'em like I see them, and hope for insight. :D