If you think people took triune just for the absorb you’re crazy. that “bit of dispel protection” is reason enough for it, it’s literally a get out of jail free card to your classes counter. The fact the absorb was so stupid good was just a really big cherry ontop.
You’re also horribly underestimating how strong slows roots and poly spam can be in a melee meta. Especially if your a caster who doesn’t have it yourself.
Fires kit is stacked. If you play another caster you’d feel it pretty fast, it’s actually so much easier then other casters outside of spriest it’s insane. That’s not even going into combust damage or the fact you can reduce the cd of combust for whatever reason.