So is the red dot useless then? I just purchased a strikefire red/green dot scope but they sent the wrong ring so it doesn't sit high enough. Should I just buy a new ring that is taller?
Not useless, but it will probably annoy you. Most people center the iron sights in the middle of the field of view, or in the lower 1/3. That's the neat thing about red dot sights or Holographic Weapons Sights like the Eotech, but if you want the dot centered in the field of view then you will need a riser or taller rings for the Strikefire.