Slayers are balanced, I think. Four slayers can do an awful lot of damage, but one slayer can’t, and that’s the balance. Four Skavenslayer-specced slayers will mow down clothies like a lawnmower vs. grass, and four Giantslayer or Trollslayer specced slayers will do the same to tanks… but slayers themselves only last a few seconds longer than witch hunters once attention is focused on them. They’re extremely vulnerable to ranged attacks, especially given that the only way they have to reduce their fury (and thus, the amount of damage they’re taking) is to attack an enemy, which isn’t always possible or prudent. There’s a serious balance there when, as a bright wizard, I can take a choppa down in 4-5 spells if he’s berserking. The key, of course, is staying away from em long enough.
The way I see it, slayers and choppas (but especially slayers, it seems) are basically AoE specced melee bright wizards. They’re tougher, because they have to get into the thick of it, and the damage they do against large groups is ridiculous. But unlike Bright Wizards, they’ll never be that great against single targets… Witch Hunters still own that aspect as a melee class. They can be passably good vs. single targets, but gain their true strength when fighting in large groups, against large groups. The Trollslayer and Giantslayer paths are good and all, but they’re like the Great weapon specs for Ironbreaker and Knight of the Blazing Sun… they’re two paths that take something a slayer “can†do, and make them better at it (DPS against a single target), but not so much better that they begin to compete with the Witch Hunter.
So, the bottom line is: if you want to drop healers and nukers like nobody’s business, without needing backup to at least trade 1 for 1, play a Witch Hunter. If you want to drop everything within a 20 foot radius of you, as long as you’ve got backup (but die like a punk if you don’t have backup), play a Slayer. Personally, I play both :)