If you think Veigar E is useful now, you haven't seen it back in the day. It was instant cast with the exact same effects. Even if you get caught inside, it's not one shot if you built properly or know how to avoid the W and/or Q.
By the time Veigar is capable of 1 shotting people, you should have the sense to counter build him appropriately or to take extra precaution not to put yourself in a situation where he will 1 shot you.
It isn't more useful than J4's ult. J4's ult allows for much utility on its own. His ult does damage to the target, it allows for stuns that rely on terrain (condemn from vayne) and it puts him right smack in the middle of the enemy team which is where you want your frontline J4.
Veigar's E does not necessarily put Veigar in a good position, does no damage, does not stun if the player knows how to avoid the stun and is actually easier to avoid since people become more cautious of it.