That would probably mean a 20% reduction to fire instead of 30% reduction as a lv3 Aqua. Spells and attacks specifically hurt summons because of the fact that they're not able to equip reduction gears. Whatever gear effects we have on at the time do not affect a summon's durability. Only our stats. Remember that single Valk Shield we wear reduces fire damage by 20%. That's not including whatever else reduction gear we'd be wearing if we were trying to fight Kasas. The mermaid is naked so to speak.Thing is, mine had spiritual sympathy 5 back then and I had Spirit Cure to boot. But like 2 fireballs from Kasa and she melts. But this was back in November when renewal had just started and a good number of spirit skills were a bit dodgey. Ventus' Zephyrs didn't work for a long time either.
EDIT: This was level 2 aqua for those playing the home game.
On that note....A fish out of the water will get burned by a stove, whereas a small droplet of water is gonna dissipate quickly after a gust of wind or heat wave. Just saying.