There seems to be a gripe with the phrasing "splitting the story", so I'd say the issue is more of cramming 2 arcs into one X.0 MSQ, not giving either part enough space to breathe. I think the main issue is that Dawntrail's MSQ feels quite rushed and not as polished as it should have been to pull this off. The fact that many think so much it is filler means they didn't get the build up right.
The fact that the second arc was the second world threatening shard-related event since EW also warrants it to have more build up. Facing Zoraal Ja as the main boss would have been enough. Establishing another shard as the source of his power could work, and then have Sphene in the Post-MSQ. The Shards are starting to lose their impact, they show up and we save/stop them in the span of a few levels. They don't feel like their own complete worlds.