With the description given, I doubt that anyone would be THAT desperate to work under him. I guess he would be beating an assistant as much as he beats metal. Even if he had an assistant, the fighting between these two would take as much time as would otherwise be gained. But that is more of a roleplaying consideration.
Just for the sake of it, I´ll have a look at the numbers.
Das Korvut might have a bonus on craft (weaponsmith) of about 11 (four ranks, +3 class skill, +1 Int, +3 skill focus), I´d say. Having him craft any masterwork item is difficult at best, with an DC of 20, so adding another 10 to the DC to speed it up is out of question.
Let me see - 40 gp is 400 sp, and 300 gp masterwork is 3000 sp.
So, an average roll is 21 or 22, let´s take the average at 21.5.
21.5 times 15 (martial weapon) = 322.5, or about 9 workdays to finish the weapon itself. I did not take into account the failed rolls. He fails about 15% of the time, making no progress 1 in 6 days. So it probably takes him one day longer.
21.5 times 20 (masterwork) = 430, or about 7 weeks for any masterwork weapon. As he fails the DC 40% of the time, this could easily add three weeks to the process. 15% of the rolls miss the DC by five or more points, so that would add 15% to the masterwork costs, roughly 50 gp.
So, after about 12 weeks and roughly 400 gp cost, the item is ready.
Now, apprentices or assistants need to beat a DC of 10 to be any help. Just any youth would probably have no bonus at all, so this is a 50/50 chance - on average a +1 per assistant, with two seeming a reasonable maximum number. So, his supposed two assistants with no competence at all to begin with, gain him a net +2 on his rolls. Even if the apprentices are moderately competent, it does not change all that much.
It is reasonable to assume masterwork tools, which gain him another +2. (three levels of expert should be good for something else than skills)
This gives him a +15 bonus.
The weapon itself is ready in 24.5 times 15 = 367.5 for one week, or eight days, with probably no failure.
The masterwork is 24.5 times 20 = 490 a week, or about six weeks (being generous here). He still fails the roll 20% of the time, so one week is added here. The cost is unchanged.
So, even with some favorable circumstances, it will take two months (give or take a bit) for this item to be ready, at standard pricing.
Until Das Korvut gets really competent assistants and even more favorable circumstances, like magical tools or something else, I don´t see that the crafting time can be reduced much more.
To be honest, I didn´t think of taking 10. This eliminates any failure chance, of course, and speeds up the process a bit. That gets him a check result of
10 +11 (skill) +2 (tools) +2 (assistants) = 25
For the weapon, he gets 25 times 15, or 375 in a week. He needs a little over a week.
For the Masterwork, he gets 25 times 20 = 500 a week. That is six weeks.
So, with a little DM handwaving, he needs seven weeks, all told. Still not much faster than before.
To really speed the process up, he would need another +5, so he can safely raise the DC. Of course, every point he gets helps a little.