Like most mana producers, I think an early summon is key to value. Yes an unavoidable ranged attack is a problem for him, but short of that, he's a real nuisance.
He needs to be kept back when possible, but he's more than worth it. If your opponent doesn't get rid of him, they will rue it. He can teleport your Mage out of trouble and his teleports are more powerful because he had Los over walls. He makes you so versatile.
Spotting hidden enchantments is also incredibly worthwhile.
I initially felt the same way you do. He seemed too expensive. But as long as he's out he gives you a mana and ap advantage. I tend to favor him in my wizard builds.
With that said, he doesn't make sense in every wizard build. If you're not reliant on tons of meta magic, he's probably not a great play.