Clerics are good to get the temple generating 2-4 mana a round, but even then, you still have to spend 8 out of pocket for a Guardian Angel, High Guard, Archer leaving little room to do anything else. This costs 9 and does 4 dice of attack and can only be harmed by melee or ranged direct attacks while a Defender only does 3 dice. And I'm not saying the Defenders are bad but this at least allows for a few more options and makes a swarm a lot easier.
There are still many many things that kill this guy: in addition to non-spell creature attacks, there's any kind of DoT (Idol, curses, poison gas, conditions from things other than attack spells, like Rot from a creature's attack or Burn from ignite or hitting a damage barrier), traps, conjurations (like Corrosive Orchid or Mangler Caltrops), incantations like Burst of Thorns or Drain Life/Soul... quite literally everything that isn't a red card or says "spell" on the ability (like Arcane Zap).
His ability isn't very good in Academy (aside from being a minor creature with 4 attack, like a more expensive Razortusk... and I guess he's harder to Stagger since a Wizard can't just neutralize him with a Lightning spell), but he's great against an Arena Wizard who depends on Zap and Wizard's Tower. That's about it, really. Most other mages have several ways to deal with him.
*edit* It probably just means Wizards will pack something cheap to counter him, like Force Push through a (Bloodspine) Wall (of Pikes/Fire) into a Spiked Pit/Hellfire Trap or something, to keep him off their Wizard's Towers. Gets trickier when his opponent is packing 4x White Cloak Knight though...
