Fire damage, still relevant

Hello,

Lurking on the forum I read multiple time that fire damages were nerfed because a lot of enemies were highly resistant.
Is this true?
How much reduce resistant should I get to have a decent build ?
For example on my shieldbreaker I want to use viper + elemental storm + thermit mines + eldrich + celestial presence.
Is it too much?

Sorry for the bad english guys.