18/30 Long Maul/Mallet or 15/33 Maul can be very strong for assisting teammates or fighting slower players with low-range weapons, but they also have a lot of weaknesses.
For one, part of how crushthrough is determined depends on the attacker's damage, so these builds need to use better holds (closer to 0.5-0.6 seconds) to make the crushthrough happen.
For another, polearm overheads are not a very long-reaching animation with respect to weapon length vs. other attack animations, and the wind-up for overheads in general seems to take a bit longer as well. Long Maul builds with high movement speed (18/27, 21/27, 18/30) compensate for this by being able to ready attacks outside of enemy range + being fast enough to move next to the opponent, but this usually means they have poor armor and low hit points, leaving them vulnerable to ranged or AGI builds with lighter weapons.
The only gripe I have with AGI Maulers is that they can really screw over people with 100+ ping, but that applies to a lot of builds. ROHYPNOL seems a bit harder to deal with now that he's an AGI 2H.