tbh, i cant think of any class in vanila (DPS) that had rotation of more than 3-4 abilities, most had just 1-2...
i think healers and tanks used more but cant really say, didnt play any until wotlk i think
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probably in first half of vanila, i think it was due to "best" build at the time that didnt put points in corruption cast time (demo/destro), so actualy shadowbolt did more dps than full run of corruption, and immolation was fire dmg while the build was about shadow (and crit) but i cant say im sure, its far too long...
i just remember there was patch when casting anything else than shadowbolt was waste of dps![]()