1. Those are not glitches. It's just how the game was put together so you don't have to have a team of all flyers/teleporters. It's a good way to keep the game simpler. Try 2 player and then you have to get 2 people across for the whole team to follow.
2. In 2, they added the Blink portals so that if you don't have someone that can fly or the like, you can quickly teleport to your base, change characters, and then teleport back. It comes in handy often.
3. Deadpool owns. When I beat it, the first thing I did was use deadpool. His voice, though, absolutely is hideous for a vicious killer.