In a series in which you have multiple ultra-villains and a good number of Lightsiders with greater overall powers in T'A'R than Slayers' tricks, his lethality is reduced and it's hard to take him seriously.

I think a lot of his villains don't come across as that scary, overall. The few who do are the ones totally out of bounds with conventional mortality, in my humble opinion, such as Shaidar Haran. I think the somewhat understandable, minor type of evil represented by the Forsaken and Slayer may have been done on purpose.

But if Slayer is scary to you, than that's all that's important in context of the overall discussion .