[Deathblob]

Assassins are sometimes useful. They certainly make your opponent have to do a lot of tedious work, and they can cause havoc if they get lucky in some situations.

Harvesters are also useful, and you can fly one geared up with a lot of MR items into a province full of a bunch of old age mages and then have it leave the next month before it can be patrolled out. Or attack PD in a mass raid, and sneak away. Or sneak into a patrolling army (with the Harvester on retreat) where you own a neighbouring province.

Harvesters are just lousy assassins because they can't move into a province without your opponent knowing they are there.