Here are some tips for Torvald’s mortars from a PC player (don’t want to argue about his utility, but if you want to play him these are some useful tips for mortars):
Now that the mortars take longer to fall using them from high ground increases the time to impact (TTI). Only use the mortars from a level plane with the monster, or even better when the monster is higher up than you. This will decrease the TTI and make it easier to score hits. The best position is when a monster is above and maybe 10 meters or so in front. If you aim your mortars correctly they will fly straight into the monster like rockets, very effective and can work against a flying Kracken as well. I am not saying this is easy to do, or can be done often, but when it happens you will wreck the monster.
A great time to use mortars is when the monster is climbing up or about to climb up a cliff either to escape or attack a hunter. This works best if you are on the ground below, but can work if you are up high as well.
You should also use mortars when the monster has limited movement options. For instance if he is at the edge of a dome chasing a teammate you can fire the mortars in a arc to the side and in front of the monster and if the lead is correct some will hit. You can also use them like Hank’s Orbital Barrage and fire them in the path of a monster focusing a teammate. The monster will either divert or take the hits.
The monster does not know where you are aiming. If a monster player is moving as soon as they hear the mortar fire, try aiming where you think he will go instead of where he is. He may just leap right into the impact zone!
Body camping is of course an excellent opportunity for a quick mortar, but it may be even more effective if used as a distraction to get the monster to move off the body in coordination with a medic or support to go in and get a revive.
Stay on your shotgun and only switch to mortars when there are good opportunities. Don’t waste time with the mortar reticle out looking for a shot when you could be using the shotgun. Also make sure you are using your shrapnel grenade regularly to increase the shotgun and mortar damage.
I recommend using solo arena mode to practice your aiming and learn the correct lead while coordinating your shotgun and shrapnel grenade. This will go a long way towards getting more hits when paired with the tactics above against a human controlled monster.