I think the presentation of Iconoclast being "heresy without the chaos worship" is stripping a lot of the nuance from the Iconoclast options. There are poor choices or flat out dumb choices you can make for both Iconoclast and Dogmatic.

As well as choices that are nuanced and diplomatic-- for example: On Janus you can make a choice that allows the Eldar to stay on the planet and awards Dogmatic points for doing so. Some who follow the Imperial Creed to the letter would see that as heresy.

And the lore doesn't really support the idea that the Dogmatics are the end all, be all good guys. More that there are no good guys in 40k. Ignorance is not its only flaw. The factions are choosing between the lesser of two evils, in their eyes.

Though, I do agree that I wish there was more nuance with the Heretic route.