Ok, now to be more serious: Having incredibly strong followers like Dyvim Whitehart back in Khrysalis (or maybe not as strong, but still significantly more impactful than a 3% boost to one stat) to help people quest through the world would be pretty nice. The more significant stat boosts would allow for worlds to be more difficult without turning away players for being too difficult. Well, unless they actually do make it too difficult. This is only a solution to general world difficulty though. One of the largest sources of "It's too hard!" for the past several years comes from the final bosses of recent worlds, and followers aren't going to be that much of a help with those situations. Sure, they'd be nice, but you're still going to struggle.
An idea I had, like just now, would be to give followers Item Cards that would be really nice for whatever tough boss you're about to go up against. Like Shadow Shield, Legion Shield, and maybe even Bad Juju for the Storm Titan boss. Or maybe they can be creative about it and give the followers cards that don't exist elsewhere. I think that that might be a whole lot more useful than a damage boost.