Description of new poison system:

hits count 0-10 calculated in this way:
count = 5 + ((cid_lvl - target_lvl) / 3.0)

poison propability 0-50%:
p = [25% + ((cid_acc - target_evade) / 8.0)% ] * spell.prop

damage:
pwr = spell.base_pwr + spell.stat / spell.stat_div

Additionally note, that sensitivity table is taken into account and it is not possible to poison pokemon, which has poison type.

spell.stat - it depends on the spell type STR os SPC of attacker

Table with spell properties in the attachment.