Absolute absorb works great versus continuous damage (firewall, meteor fire) or a big number of small fire attacks (hydra, Diablo's fire snakes), even if it's a seemingly small number. Continuous damage is dealt once per frame and absorb works on a per-frame base, too. That means, with 15 fire absorb you can effectively ignore 750 continuous damage per second (because you get healed by the absorbed amount).
As long as I can't afford the Tal Rasha set for my sorc, she wears the Rising Sun amulet which has 0.75/L fire absorb together with perhaps 50% fore resist . Neither the Councils' hydras nor the spells from the Bloodlords in hell Durance 3 can harm her - in fact, most of these attacks heal her.