That’s a fair summary, but I’d have three counter-arguments.
The first is that, in my experience, it’s rare for heroes to be limited to mid-die Attacks. Even in Green, they’re usually either doing “Attack + Something Else” or “Max Die Attack” or even “Attack that ignores Defend”, and they’re often benefiting from Boosts, either P/E ones or just general ones tossed up by teammates. So I’d generally expect the baseline to be higher than a 1-pt difference on the first Attack.
The second is that rolling a single d8 instead of a spread means that the Berserkers are far more likely to be on the high or low end, and being on the high end doesn’t help their defense. It only takes a single 1-pt Defend to put them in a position where they’re getting battered.
And the third is that they’re pretty Hinder-vulnerable. Since they’re using the result of the Attack to Defend, a Hinder hits both numbers at the same time.