My gym has a pro boxing coach, and I was watching the other day as he held focus mitts and trained a fighter. I was also recently at a martial arts school and watched a Tae Kwon Do instructor hold focus paddles for a student as she did various kicks. I was compelled to ask myself, do focus pads help you or hinder you?
Clearly you train with pads, mitts and bags to improve accuracy and timing. When your opponent presents a target to you by moving and/or striking, accuracy and timing help you to react with the correct technique at the right time to the right place. If a boxing trainer presents the focus mitt by only staying stationary and holding it up, that is not likely to help you. If the trainer moves and simulates a punch that will actually hit you if you don’t move (for example a Hook that you have to duck and counter), this is better.
But, either way, the timing is different from a real opponent because the trainer must retract and/or place the mitt for you to hit it. This is slower than what happens in the course of a real fight and may adversely affect your reaction time. One fix I have seen is to start with the first pad in place and quickly move the second pad into place, but this is still too slow.
This brings me to accuracy; Is it helpful to have a person stand in front of you and hold striking pads away from his body for you to hit? Muscle memory is important and is learned from hours of drills and practice. It stands to reason that if you practice hitting a pad held away from a person instead of hitting the person, this may adversely affect your muscle memory and therefore your accuracy in the ring in the long run. It is better to get high quality protective gear and heavier, padded gloves and spend more time with sparring partners so the timing you develop is based on a more realistic opponent.
With Tae Kwon Do the same issues are there, but the kicking drills accentuate another bad aspect of using focus pads; the recovery phase. It may look good to have someone hold pads for you as you expertly do two or more kicks (which helps you to be more comfortable with combinations) but what you do after the combo is important. If you land awkwardly or you have to move or step to get into your fighting stance to face your opponent, you are setting up bad habits. If you pause or drop your guard after your combo, you are setting up bad habits. A similar thing happens when a boxing trainer steps away to reset and the fighter drops his guard.
I also noticed that some of the drills lure your focus to certain techniques and neglect the Muay Thai and Wrestling techniques (specifically leg kicks and takedowns) that can be done to you during your attack. This may be okay if you are only going to compete in boxing but is not helpful in Mixed Martial Arts. It is better to spend as much time as you can in the most realistic scenario as possible.
Do in training what you intend to do in War.