After playing with Ninjask for some time, I will say that it's a pretty cool mon. So much so that I built a team around it.
Jask's biggest weakness is its inability to take on Rock & Steel-types without resorting to techs such as Power Herb + Dig. Thankfully, Ninjask acts a great enabler to wallbreakers that can adequately break through those sorts of Pokemon, and that's where Gallade comes in. Additionally, while Gallade might not have the stat spread for cleaning, it can punch holes in teams with little to no effort, to the extent where either Jask or Sneasel can clean up afterwards. Speaking of the latter, Sneasel acts the team's primary Psychic switch-in and secondary cleaner & speed control. Being faster then Charizard, Psychics, unboosted Silvally formes and the like works wonders in this meta, and Sneasel has the STABs, movepool and power to take advantage of how PU lacks speed control outside of Scarfers (which are rare) and naturally faster mons (which are even rarer and are lacking in viability outside of Whimsicott, Ribombee, the aforementioned Ninjask and arguably Jolteon).
Regirock is chosen as the rocker of this team in order to better defensively handle threats such as Glastrier, Aggron and Lycanroc. Thunder Wave also helps it cripple offensive threats and more easily apply pressure then its competition, Gigalith. Eldegoss does Eldegoss things. It spins, puts a mon to sleep from time to time, forms a decent defensive core with Regirock and acts a cleric, with the added bonus of letting Gallade play more aggressively in the earlygame. The EV spread allows it to outspeed SR Sandaconda while being able to 3HKO utility Jellicent. And Togedemaru is the defensive check to Fairy and Psychic-types, as well as the Wishpasser of this team. Being able to use a somewhat slow U-turn to lure in Ground-types and pivot into Elde to restore HP via Regenerator comes in handy as well.
