I use mine all the time, either a a regular Grinder or as the plague hulk variant.
Generally i like to drop mine in close to something and vom them while i shoot them, but they aren't bad as long range artillery if running as a regular grinder, especially if you can find them a ruin or battlement to sit on.
Plague hulks aren't bad either. Better for close in work and
IIRC they lose the skyfire guns the regular grinder has, but they can take a hit