It does seem to be a very common theme with AP's going all the way back since Unholy was introduced. A little less back then since you had tons more players to build it back up, and a pool of AP's to steal their weapon and leech. However I do agree that unholy weapons are high risk/high reward. Also to be fair I have never gotten an AP up to unholy so take the thought with a grain of salt.

However the idea/suggestion I have would be something like "Blood(Or Soul) Sacrifice. An AP could sacrifice a piece of his soul and imbue a weapon with a bit of his OWN soul. This would make you lose your top tier control down to the level below. This could be perm, or just require them to build it back up with PK kills. Also, the cavaet would be if THIS weapon is destroyed, you now lose 1 or 2 con since it was a piece of your own soul.

Just thoughts, to make it not as horrible and a path to jump start back up since it would be hard to get 30-40 kills at hero with a lower player base