1v1s against average arch players are pretty easy, 1v2s are harder, and 1v3s-1v4s are just madness. Obviously you can use a fireball in a 1v2 to kill them off of fall damage, but in a 1v3, that's harder. A solution is to bring a teammate, but if they dont listen you might be out of options, unless someone responds to this post with an answer.

   Tip 1. Use a knockback stick to hit them off the map.

   Tip 2. Use fireballs to knock them off. 
   Tip 3. Circle around them to swap positions, get their bed and circle again to get back to your base. 

  Tip 4. Just get better at PvP.