Hm, no. Most common answer to Steamie is Mind Flayer/Ulitharid, and you mostly see both in controlbows. Reason being they both grant a lot of value in one card. Another common answer is Fire Bolt, as decks that pack 'em always get 10
or more. Rage Elixir isn't as common but a very strong CC card that would be used more if it wasn't overshadowed by Fire Bolt.
Your comparison with Dragons works against you.
This is the best vanilla dragon in the sense that it gets +1 health than most Dragons since they sit at 10/5. Paying 4
and 6
puts you at 15 damage done, 12 attack and 10 quanta spent. This is balanced by the fact that Steamie succumbs to lobotomization, Reverse Time (RT is also strong against Dragons though) and forces duo quanta usage.
Your argument focuses on Lightning not being able to kill this in one hit. The unupped meta needs 6 HP (and more) to balance out Lightning as it kills every single unupped fast attacker in the game. It's why you see Phoenix+Steamie decks combating the very common Lightning in PvP. Reducing Steamie HP would not be good for the meta.