At the moment the problem with this arc is that there isn't a real threat.
The villains are literally 3 and honestly they don't feel like they are Top Tier guys, vs:
- a Yonko crew that includes Nika, Zoro and Sanji (top YC tier or above), and an ex Warlord,
- the whole Elbaf village with 2 of the strongest giants ever (Dory and Brogy)
- the Left Hand of the Pirate King
- probably THE strongest giant ever (Loki)
It's too one-sided for the good guys at the moment to feel some real tension, and the nightmare illusions are Numbers-like fodders.