you mean from mage to (demon hunting) mage-warrior to demonic mage-warrior to redeemed mage-warrior to Titanic Mage-warrior.
Illidan was never a druid, melded magic and swordsmanship from day 1, was never a warlock. And though he is a demon...thing thats not exclusive with classes (hence allt he eredar who are warriors or mages or warlocks but ALSO a demon). And the Titans are directly tied to nature and the Light, not to mention Illidan's race is titanic in origin.
Not saying they should do it but you are makign it seem more complicated (and inaccurate) than it is.
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I doubt broxigar is a live as getting non magic beign sbeing impaled on giant swords tends to be fatal. Its good to know that the person who DID this though is more powerful than the person who took ner'zhuls soul and turned it into one of the strongest forces on azeroth.
I dont see any reason why they wouldnt be torturing broxigar's soul for over ten thousand years.
Though i thought Brox was in Valhalla?