Imu is still fighting like before, using Firearms,
He fired a gun at Zoro & used Explosives on Hajrudin, Gunko's Ice & Sanji,
It's clear that Omen is weaponized Abyss Portals,
Oda literally explained Zoro's mistake in the previous Page with Stansen's Warning,
But apparently, He was still able to react in time, try to block with his Swords & avoid a Headshot,
Once They understand how Imu's Powers work, They can perform better against him,
But his Real Threat comes when He decides to unleash Mother Flame through Omen,
I don't know how They will deal with that,