I've noticed something with my revisit to the patch that does not appear to be reflected in the guide - it seems that the aura that bosses have (pack Uniques, not Act Bosses) will switch if you leave their radius of awareness and come back. I've noticed this a couple times when I've run my characters away from a Fanatic pack (because it's a ridiculous increase in difficulty in Hell, as IS discussed in the guide), and come back to find the boss with a Might or Conviction aura. Is this something that anybody else has noticed? Is it still the case for 1.10+? It's been too long since my previous foray into the game for me to remember.
I think I've only seen this happen with Fanaticism specifically. I can only recall seeing this happen with SUs, so you might be right about that. But I haven't tested extensively.
Though, I don't think that it necessarily has anything to do with awareness range:
FYI it even happens for me when teleporting straight towards an enemy, so leaving/returning is apparently not how it necessarily happens.
I remember one instance specifically when teleporting straight towards Rakanishu, and he had two auras active for a few seconds, before dropping off Fanaticism. I had already explored the map, so I really was going straight for him without ever leaving his awareness range.
I think the bug may be more like, the moment they spawn, they spawn with Fanaticism as some kind of default, before it is actually determined which aura they will/should get. If that makes sense.
helvete mentioned that this bug exists in all patches, but I can't recall ever seeing it past 1.09 myself. Perhaps it's a LOD-only thing (I played Classic mostly from 1.10 to 1.14).
BTW, it seems it hasn't been mentioned that you cannot buy mana potions in 1.09. That appears unimportant at first, but casters can run out of mana more easily in 1.09 because there's no Insight runeword.
Should've been mentioned, I agree

in 1.06 and 1.09 I've done plenty of
mana potion runs.