Kuku: Two skillshots, ult is easy to dodge.
Scylla: Root ends on 1 before 4 is wound-up, most of the game. Difficult to hit Scylla's ult without a team.
He Bo: You forgot his third ult. The trade off, however, is that one of his attacks is a skillshot, while the other two require him to be in close proximity to the enemy, with no escape.
Ah Puch: No escape. Pretty decent range and extreme burst potential.
Anubis: No escape. Not burst. His damage is DPS. A lot of DPS, but completely shafted by player skill in most cases. If you miss the wrap, you'll miss half his damage as well. If you can't aim his ult... useless as well.
Nox: Tiny AoE with a wind-up, requiring a lot of skill to land it consistently.
Zeus: No escape, skillshots for damage.
Vulcan: Not a great escape, and his abilities do not combo well. Meatball can knock enemies out of his turret range if you're bad with it.
Ao Kuang: What, an assassin-like mage has bursty kill potential? You don't say.
The problem with Raijin is how EASY his crazy burst is the land, and how TANKY he is at the same time.
2 + 3 and you've killed anyone that isn't building Bulwark of Hope or Genji's Guard. 2 + 1 and you've cleared the wave and probably poked the enemy mid laner for a sizeable chunk of damage without even trying. 2 + 4 and you've deleted a whole team.
"Utility" mage.