Time to be a keyboard warrior today.
A lot of new players are using axes, clubs, staves etc. I see a lot of players using staves and then pass to samurai and if they want to continue playing they look for daggers or swords. Having the 3rd class also be exactly the same just makes the game easy. People are going to continue if they like the game, not if the weapons are the same for the first 3 classes.
This is something I vehemently disagree with. With any game, especially a game like this, you want your game to be easy in the beginning. You want people to sink time into the game with ease at the start. They need to feel like their time invested is worth playing more. This is basic Sunk Cost Fallacy stuff. This is why people who buy skins on League of Legends keep playing, or people who spent months getting mounts in World Of Warcraft keep paying monthly. With the sword classes first, and them being 3 doors, of COURSE it's supposed to be easier. It makes complete sense to me.
What happens to all those noobs that hit 4-door monk, can't pass their mq, are stuck using robes and have a hard time soloing? They quit. Paladin with 4 doors in place of monk would be a great solution. Get stuck on paladin and you have a class that has many weapon choices, armor choices and can handle soloing better for new players. Get stuck on monk and quit. Pass from monk to ninja and realize it's the same thing but different abilities and quit. Changing this would bring forth diversity and be more beneficial for new players than harmful.Dude there are veterans that quit after failing enough on monk. That's just this game in general. With 4 doors it gets that much harder to pass, and being stuck on any class makes it that much harder regardless. We can't base these kind of changes on how hard or easy it is to solo, as this game is intended to be a multiplayer game. You're supposed to get some buds and slay some mobs in the catacombs. If the argument is that it would be easier to solo, and that would be the benefit of it being on 4 doors, I would defer back to my original point of the earlier classes SHOULD be easier to solo, making swapping of the class placements detrimental to the player experience. Sticking a harder "Solo" class closer the front is counter-productive to keeping players.
Those noobs who buy staves for rogue can now use them on the 1st and 3rd classes. Those guys that have swords can use them on the 2nd and 4th classes. Noobs who buy clubs because they're cheaper can now use them longer. It makes much more sense to split monk and ninja with something different 
.I actually understand what you're trying to get at here, but I think you're thinking about it wrong. Think of any game you play. The cheaper the gear, the less effective they are in their longevity, correct? Buying cheaper gear is more beneficial when you're in the easier part of the game. When you start getting further in, you need to upgrade your gear and spend more on it. The only way to do that traditionally is behind a pay wall or by grinding out the easier levels for later level gear. And once you unlock that gear, it's good that you have gear for the next two classes then! Having them be somewhat similar lets the players investment not feel wasted for 1 class.