The 5 best in my opinion are Abyss Cannon, Gun Deck, Mortal Skewer, Plank Walker, and Blow The Man Down. This can be an enemy flanking you, targeting the enemies healer, or destroying a deployable. Finally the best situation for Harpoon is attacking one exact person. This includes firing at a contested payload, creating a wall of mortar to deny entrance of a very large area, predicting an enemies movements, and if you're using the Crow's Nest card, movement.

The next best situation for mortar is for area denial.

Some examples are when your team is moving the payload, when you are attacking someone that is very close to you, shooting off walls to get around shields or other obstacles, or when the enemy is moving around alot from a bit away. To begin I'll talk about the situations best for those attack types with the situation that is best for using the mortars is normally best against there is a moving enemy or to get around deployable shields. Dredge has 3 different types of attack, all of them for different situations along with unbelievably good cards and talents. Dredge in my opinion has most potential out of nearly every paladin in the game currently.

Paladins dredge harpoon deck