@Ravok9
Greetings,
It is indeed possible to beat Medium Difficulty bosses without Baton Pass and it is also possible to beat Hard Bosses without Baton Pass. You might have to play with Stall Teams or with specifically developed teams for each boss. If you want to keep almost your entire current team but you want to speed up your Boss Fights, you can switch your Furret for a Gorebyss or Huntail with the moveset Shell Smash, Substitute, Baton Pass and Protect/Aqua Ring, up to you. The change from Furret having to use Coil 4 to 6 times and Agility 3 times to Gorebyss or Huntail using Shell Smash 3 times is of around 6 less turns and will save you a few minutes per boss fight. It is up to you!
Kind regards,
Kvar