IMHO, people don't do well with DKs because they expect to get to 50 and have some super powers that will rock the PK base.
Dks are super-strong at their peak, but you have to go thorugh a lot of pain to get them there. This is because all the powerful DKs were taking full advantage of malform. Face it, malform weapon is the signature spell of the class and I haven't seen a DK who has managed to get one to lvl 10 (did Waojin?) let alone keep it long enough to deal out the pain the class is known for. To get a malform to the level where a DK truly will dominate requires PK skill, knowledge of the class and a decent invest of brains and time.
In my case, I condeathed a DK without getting past lvl 5 malform. It wasn't until my second DK that I saw a lvl 10 malform.
To be honest, the one significant change to lvl 8+ malform has made the class a whole lot less fun to play. If the spell (and its effects) was too strong (and after I'd had lvl 10 malforms I thought that it was far too powerful) the effects of the spell should have been toned down. This hasn't happened, the spell has been 'balanced' in such a way as to make any lvl 50 DK someone who has to go through a huge amount of pain on a regular basis (ie when ever they die) just to get the most out of the class. IMHO, why would you even bother when you can play other classes that are easier to stay alive with and are easier to extract the full PK potential out of? Malforms are cool - yes. They aren't that cool though.
My suggestion:
Change that 'property' of 8+ lvl malforms back to how it used to be and tone down the actual damage the weapon deals out (no idea how its coded to be so much so I can't say how).
Cheers,
L-A