It seems to me that any MMO developer with both PvE and PvP in their game spends a huge amount of time trying to find the right balance between these two types of gameplay. Customers, regardless of their preference, often find their favorite content being rebalanced in ways they don't like because of the development teams need to balance these two types of content against each other. That seems to lead to a lot of wasted development time for the company as well as irritation for the customer.

Here's my solution:
Zenimax should duplicate all PvE skills to create a PvE version and a PvP version of the current skill list. They would be balance separately without affecting the other, so the devs can tackle the unique types of gameplay in the most appropriate way without having to worry about hindering the other type.

The PvE skill list would automatically be the list available in PvE zones. The PvP version of the list would only be available in PvP zones.

To take it a step further, all skill points earned by the player would be duplicated to each list (I.e. You earn 10 skill points, you will have 10 available for the PvE version of the list and 10 available for the PvP version of the skill list). You could then assign the same number of skill points to each list, but picking and choosing only the skills you want for that type of content. Different skill load outs for each.

All in all, what you're looking at is all of the same available skills, just duplicated and balanced separately to create a better situation for not only the customers, but also the dev teams because they won't have to consistently correct loopholes in one type of content the resulted from fixing a loophole in the other type of content.