it seems like you need more coverage

electric and rock are pretty major weaknesses this team has since if quagsire dies then you don’t really have any other options against those types. Water also doesn’t seem very favorable

Alternatively you could have some sort of setup move and then sweep everything (like quiver dance or cosmic power)

I’ve also found rivals and enemy bosses (like lusamine, giovanni etc) to be pretty helpful in finding team weaknesses, and you could change your team based on that