The Malefactor base class is a two edged sword. It lacks enough power to be really effective on its own and its debuffs benefit other classes quite a bit (wizards, sorcerers and witches especially) but in a group they will always be apart because they are too dangerous to the group when they are close by (benefiting enemy spellcasters).
The idea of a character that has been cursed in some way, and who uses that curse to their advantage (most of the time) is certainly different from most and I think this class has a lot to offer a group that other classes typically either can't do or can't do very easily. In the right party I think they could make a big difference by making it easier for the party's spellcasters to affect the enemies, but care must be taken to not affect the Malefactor as well, so I think this class would work better in an experienced group who works to maximize the advantage vs a group that doesn't understand the ramifications of battlefield placement. They don't get evasion or improved evasion, so they will need some protection of some sort if the sorcerer wants to drop a fireball on top of them if they get surrounded for example. And the Cleric will not want to spend much time next to them when they need healing since their save penalty (the core ability of the class) affects everyone in 10 feet.
The writing is good, and the concept is pretty solid, so I'm trying this class out in the next game my group is playing, where we are starting out as zero level dwarves, and in the first session my character was cursed and blinded (this was just before this class came out and I was trying to decide what class he could still be effective as with that drawback, so this seemed like a pretty obvious fit).
[4 of 5 Stars!]