Class locks, great idea. When matchmaking, connection speed/proximity should be priority, followed by classes. Reducing teams composed of the same classes will help players take advantage of each classes unique abilities/traits.
Now I’m sure this will be unpopular, but every class should be able to tackle every kind of threat. This is an essential element in a game that depends on putting four completely different players that have never fought together into the same lobby. While each class has unique abilities and traits, classes should not have their inventories pidgeonholed to fit one specific combat role.
Classes that are too specific often suffer greatly in practice. What may look great on paper at tackling a specific threat often falls short because it does not account for the random chaos of Darktide.
Take for example the fan favorite Crusher ambush. Crushers are often quiet compared to the background noise of combat/music and blend in very well to the often dark corridors of Darktide.
In a split second, disablers blitz out of nowhere and remove the vet. While the vet is netted, the crushers stride forward and ensure he can’t be freed.
Now, if this were a game where classes were pidgeonholed by talents and inventory to the extent OP wishes, the team would more than likely be royally f***ed to put it lightly.
Without the Vet’s Brittleness debuffs, Krak nades, shout and Plasma gun the team would be at a significant disadvantage. Remember, in this scenario classes are locked at matchmaking so there’s only one Vet. Now, this is an extreme example but the reality is when there’s limited communication and organization in a game as hectic as Darktide it becomes very necessary to round out classes a bit.
That being said, OP is right about Dueling Sword on Zealot. Some weapons (emphasis on some!) should be class specific. Psyker’s unique class traits - high crit, low toughness - fit Dueling sword perfectly as they allow a Psyker to maximize their crit potential while using the Dueling Sword’s high mobility benefits to avoid taking too much damage to their already limited toughness pool.
However, when given to zealot - a class unique with the highest base mobility and the most melee focused damage talents in the game it becomes absolutely broken. It becomes a matter of needing a nerf, but reducing mobility bonuses or crit bonuses will definitely make the sword a significantly less valuable option for Psyker. While removing Thrust and Rending could also be an option, the most logical is to just keep DS as a Psyker specific weapon.