True enough, very good points. I can appreciate the idea that you are not supposed to be able to "hide" in an arena. So hazards aren't actually meant to be "terrain" in the sense you might see in other games of this type. If you put a big stone wall in your arena, you're doing it wrong. All hazards in the arena are meant to be open hazards, as per my suggestion above. Even the stone pillars are just meant to represent something that you can bash someone's head into, not something you can hide behind.
I'm very satisfied with that answer, but would suggest that it might be a good note to put in the rulebook somewhere. Both about models and hazards really. Just pointing out that attacks and abilities are not blocked by either intervening bases or hazards, and in the terrain section, note that the hazards are intended to hinder movement and be dangerous, but not block attacks across them. (Which is why they are called "hazards" and not "obstructions".)
That would get the point across to the readers from the beginning, rather than being something that you only realise after you have already built a bunch of ten foot tall concrete walls (intended to stop Zahra from attacking you) for your arena.