Rule of 3 applied to Detachments impacts Empire negatively, it’s already not a great rule to begin with.
I completely agree, but then, I think detachments are already terrible and not really worth taking.
Meanwhile, Empire could bust its 700 points with a Griffon general, Level 4 wizard on a Pegasus, and a BSB on foot
It's tight, but my configuration for these guys comes in at 695 points. I think these are all 'must take' characters for the empire basically.
I get it if your list already fits within these
That's basically the case, yeah. A couple different lists all more or less fit.
Mind you, I don't think those comp restrictions really add anything or fix anything either. I don't feel they are improving the game. But I also don't think it's very hard to make decent (for the empire anyway) lists that fit within those criteria, if it's important for you to go a particular event running them.