Let's fix the Poison-type

Current failings:
-Weakness to ground, earthquake is sudden death
-Steel types are immune to the damage
-Toxic is preferable in almost every case
-Poison-type moves are weaker than their alternatives, e.g. Poison fang is weaker than thunder fang and other such moves.

Possible suggestions:
-Make every poison status follow Toxic's model of increasing damage each turn.
-Make moves like leech seed deal damage to the opposing pokemon, essentially giving all Poison pokes the ability Liquid Ooze.