ignite always gets removed before poison.

use a fire main high chase combo with koh, poison is applied last and removed last.

use a water main with poison tai and itachi, poison is applied first and removed last. shark bomb with kd to high chase then itachi will chase for ignite

i think it was coded to do this because ignite stops healing, poison doesn't, so this is the better order for healers who are the majority of cleansers anyway. if you had 2 healers who cleanse 1 debuff each then its better for them to cleanse ignite with no healing then poison and heal instead of poison and no healing then ignite and no healing.