Past experience tells me when they say "balance changes" they mean "nerfs galore".
Rather than crippling existing characters, which people have invested time and effort in (including PotD, Iron mode etc.), by ruining their abilities that are somehow "imbalanced" (in a single-player game, yeah right), how about buffing classes that are currently made of suck and plainly uninspiring (looking at you, paladin)?
TL;DR: instead of weakening good classes, how about strengthening bad classes? That way everyone wins!
I agree with the general sentiment of buffing bad classes rather than nerfing good ones, but why is it illegitimate to balance in one way, based on the argument that it doesn't need balancing in a single-player game, yet legitimate to balance in another? Your argument makes no sense. If you said that balance didn't matter at all in a single-player game, you'd have a point - I'd disagree and argue against that point, but it'd be there - but first suggesting that imbalance isn't a thing in a single-player game and then call on balancing is nonsense.
I think you missed his point entirely.. and he makes a good one. Instead of nitpicking what he said in parentheses, please read his post again and try to take it in context.
Instead of nerfing classes, buff the weak ones. This can work for singleplayer games, since it's only YOU playing and other people playing other classes will not care as much as in multiplayer games (see guildwars 2 forum flooded at the moment with turret engineer nerf posts and everyone calling for a nerf except people playing a turret engineer). How many people are calling for class nerfs in singleplayer game forums? Sorry if I made this sound too simplistic, but this way it can be understood.
Most importantly with 50+ hours in your character will not be gimped all of a sudden (especially in POTD).
So I wholeheartedly agree that this approach is better. Don't nerf classes, buff the weak ones.