If it works that way in normal rs i feel like it should be the same for runex, they most likely just forgot to code in the shielding properties to Olms unique venom fire for the ancient shield
Just posting a glitch found in game that the wyvern shield anti fire ability doesn't work against Olm's venom fire in the raids like a dfs or lava pendant would. Hoping it'll be fixed soon so someone else doesn't make it to the end and get 99'ed like me cheers.