I see. I agree that there is a danger of people taking this guide as a guide on who to ascend - it was never meant to be that.
I created it in an attempt to show which positions are the best for certain heroes because I cringe whenever I see MN in the right corner, for example.
(New) players need to focus on offence first and then think about defence.
In your example, if a player has both Bera and Zulag, I would never recommend ascending Zulag before Bera.
But for players who don’t have Bera and have ascended Zulag because they had a lot of tabards and no better option, she would be a really good tank, who does not depend on particular heroes to be effective.