Hexproof on a land generally isn't that useful, especially with the current views on land destruction. I could see a cycle of dual lands with hexproof being sensible, though.

There is a lot of land destruction in the set. In a set with 4+ land removal options, would a dual with hexproof be too powerful?

Before we can answer that I think we first need to understand: why is there a lot of land destruction in the set? I assume you aren't intending to make a Ponza-style deck with 8+ 3-mana LD options viable. So why does the set have all this land destruction?

From how you said you're making these cards, I might guess the answer is something like "because a lot of events in the book map to land destruction in Magic terms". Okay, if you want the feeling of playing with this set to involve a lot of events that feel like lands being destroyed, I guess that's fair enough. In which case I think it's fine for there to be a number of lands with hexproof (at a bit of a higher power level than this one). Given Blossoming Sands, I'd say an Elfhame Palace with hexproof would be just fine.

Fair enough.