there was actually a talk about making it shorter.
at first, there would be 5 or 6 Spriggans but they decided to have 12.
IMO, he should have made 5 of them.
1. Ajeel
2. Brandish
3. Dimaria
4. August or Invel (August more but not making him related to Zeref and Mavis)
5. Irene (that backstory was quite good and her design was

)
it would have been much better.
and Zeref fight wasn't rushed, more like it was incredibly bad decision to have that fight in the guild with Natsu and Zeref wasting panels of several chapters (a dozen or more iirc) throwing dumb magic punches.
you can a make an epic fight with 2 chapters or even 3 instead of wasting that.
Acnologia's fight wasn't rushed either tbh, more like that Rift of Time was way too conveniently pulled out of nowhere alongside Anna not to mention he was chasing a ship for quite a while.