You raise a good point.

In OWPVP games, PvE can't be designed to be too challenging in itself when players are intended to compete for it. Otherwise you'd be developing an expensive content that only a minority of players will ever get to experience.

There's a reason modern MMORPGs have a lot of instanced content and use personal rewards system so the open world PvE is players (plural) vs environment. Players can only cooperate, so the PvE can be designed to be more challenging in itself.

I hope there will be enough challenging and meaningful instanced content to keep players that don't care about contested content entertained. Otherwise they'll be mostly left with gathering stuff and hunting common npcs.