Most players already do the 24-man content anyway considering that in the odd-numbered patches, that's how players who aren't doing savage unlock the option to upgrade their gear as well as get gear for alternate jobs.

Early on there might be some bumps, but I've only ever seen a handful of times where a group was unable to clear the raid and get the rewards. Making them a part of the story adds to them since it makes them more relevant. It's not as though they're asking you to clear something like Titan savage to advance the story. They make easier versions for people who want the story and harder versions for those who want the challenge.