Really the problem isn't with Zephrys so much as it is with Avenging Wrath. It's basically the only card that double as both a board clear and as burst damage, so Blizzard is going to have to really rework the programming if they want to find the situation where it can be used as both.
This isn't necessarily true. Arcane Missiles and Greater Arcane Missiles do the same thing, as does Spreading Madness. There's a number of effects like this throughout the game. Maybe not many between basic and classic but since Arcane Missiles exists as well, this necessitates an adjustment to the coding in my opinion.