30k mechanicus is a massive pain (I have a local player who loves it, and I'm kinda getting into it

)
Although, I've noticed that if you can get them into
CC, dreadnoughts really put a hurt on most of the "common" mechanicus options. multiple S: 10 attacks that negate mechanicus toughness and armor save, and an
AV that is only hurt when the big ones opt to use smash.