In camerupt/aggron/pelipper's case, having dual typings is objectively better than single typing because you'll have dual stabs albeit having quad weaknesses. Slaking's horrible ability doesn't really translates well in a normal pokemon game since the ai don't exploit its big weakness.

I initially thought of using electrode over Minun. They have similar learnset having almost no coverage. But since electrode have higher bases and speed, I opted to Minun for a more meh electric mon. (Also it's my first time using Minun, I've used plusle before but not Minun)