Van Cleef got tired of his doors being used for cannon target practice. Your base will make a fine substitute.
Try to go to the left lane at the start when the target markers are moving to the left. Siege Minis deal 2x damage against the boss. Unbound Minis also work well against the boss!
For every PvE mission, there is a campaign version and a Heroic version. When you first begin the game, you can only participate in campaign missions. Upon collecting 50 sigils, you will then unlock Heroic missions.
Campaign missions will grant rewards after the first successful clear with ANY family. Heroic missions must be completed with EACH of the 5 different families in order to receive the mission rewards.