Is it a different storyline with different bosses, similar to the difference between Normal and Hard Mode Dungeons?

or is it the same storyline, and same bosses, just more difficult, like Normal/HM/Extreme Primals?

I'm asking, because I am probably never, ever going to be a Savage raider. for the most part, I dont have the skill nor the patience to deal with it, and I'd just like to know if I am going to miss out on any important storyline by only doing Normal Raids.