So does this mean that all four explorers aren’t getting hero cards?
Why would you assume such a thing? This is an E.V.I.L. reward. It has nothing to do with the rewards from the Explorer path.
I was assuming this because the fact sheet for this adventure said that they will be releasing 35 cards, with four of them being legendaries. If Reno is one (Mage), and this is two (Neutral), that leaves two legendaries left to be split amongst Druid, Hunter, Paladin, and possibly Neutral again.