I was looking for a similar PrC at one time. The Occult Slayer was initially presented as a gladiator PrC in an issue of Dragon, which may be why some of the abilities seemed odd to Inconsequenti-AL. It's certainly not a "hunt down and kill them" type of class. The Mage Killer from MoF was also not what I was looking for either, although I forget why exactly. I think because it was exclusively for spellcasters.
There was a psion-hunter in an older issue of Dragon (the one focused on the original 3E PsiHB) by Monte Cook that could be "flipped" to be a mage hunter instead (by simply changing instances of "psion" to "mage," "psionics" to "magic," etc.).