I… actually agree with everything you said. Plasma is really solid, and Fire is just. overshadowed by the most overpowered magic in the game (shadow (please nerf shadow it is still braindead op))
Fire is good in certain builds (i.e. Explosion mage for the stun) but is usually just… eh.
poison is good for sustained damage on something like conjurer, because it basically removes the opponent’s regeneration for as long as you’re fighting
on it’s own it’s kinda eh, it works but it’s not that great. but with conjurer imbue you get the bleed synergy along with higher damage multiplier, so it’s great for applying a high damage long duration DoT
(until you fight a wind mage)
I know I sound like I’m glazing it a little but once you land a high damage ult art blast on your opponent, they start taking MASSIVE DoT which can easily be prolonged by things like surge