I know this is like a taboo subject, but I have a couple of points that I think would make DKs much more popular and viable as a class without making them overpowered, or even substantially different from the way they are right now.
The main problem I perceive with DKs right now is the way their malformed weapons decay when left on the ground (from being disarmed), or in their corpse (after pdeath or mobdeath). From my personal experience, the ease with which weapons decay is very disproportionate to the difficulty of powering them up through PK. I will use an example that occurred with a recent DK of mine to illustrate this point.
I had a malformed weapon at lvl 3, and I died to a shendiir or something in S'handor. My hometown was Miruvhor, and after dying I made it back to my corpse in about 1.5 minutes. By the time I got there, the weapon had totally decayed back to lvl 0.
By that example, weapon decay occurrs at almost one level per 30-40 seconds. In contrast to this, it can take several PKs for a DK to move their weapon up in power even one level (at higher weapon levels). This is certainly a very laborious process, and can take days or even weeks to achieve. A mob death for a DK is, when considering weapon decay, just as terrible as a PK - sometimes even more so. DKs are a high offense class, not a highly survivable class like communers and some mages. Mob deaths are much more likely to occur, and in places like Winter, Gear, or even just a spot far away from your temple the effect on your weapon can be very serious.
My Suggestion:
Make it so that malformed weapons do not decay after reaching a certain lvl of power. Perhaps at the stage when the weapon gets it's own special name, or when it becomes unsaccable. I don't feel this overpowers DKs in any way, as getting a weapon to that lvl is quite a feat in itself.
Right now, even fully malformed weapons decay on death, which I feel is a bit harsh on the DK. It's not just a matter of the DK's strength in PK, either, as weapons decay just as readily if the DK dies to a mob. No other class in the game has such damning consequences for a mob death (certain qclasses omitted). When you consider that the DK is a class with no protective shield, castable sanc, castable word of recall or a major cure (which I am not suggesting they should get), it makes them more likely than a lot of classes to die to mobs, with far harsher consequences.
I just think a single moment of misfortune or a lag spike resulting in the loss of days of work, and many, many PKs is a bit much, and could be easily changed without overpowering DKs as a class.