Regarding Veigar's E and how to make it better defensively and have counterplay for the enemies.

Why not make it something like Anivia's Q in the sense that he throws out a projectile which he can then detonate to summon the cage? This would provide the enemy with a visible warning of the incoming cage, before it is even on the ground, yet at close range would let Veigar have a more reliable and instant stun to fight the likes of Zed who, in Veigar's current state, laugh at the wall and simply teleport over it while it phases in, or just save the jumps for when Veigar does throw the cage down.