you basically have to make auto attacks very strong.

Why would this require auto-attacks to be stronger? I don't think that the average player (apart from the very lazy. Yes, I know those exist.) is only (supposed to be) using auto-attacks. I think that most players like to use their (impactful) skills. What makes it hard or rather makes a huge difference in DPS is that timing matters a lot, e. g. Blight stacks and their consumption on Harbinger.

I'd also assume or rather hope that less experienced players are making slightly more defensive gear and trait choices which allows them to make a few (minor) mistakes during the course of a boss fight without getting downed or being a constant burden for the healer, i. e. trade some (max) DPS for more survivability.