I have to admit that when the interval gets too tough for me I add the fins to keep up, but then I am trying to keep up with the kids who are seriously much faster than me. Coach is ok with it since I need to learn to use my legs anyway (I'm a leg dragger!).
I do agree that masters swimmers need to learn to leave 5 seconds apart. When I used to swim with the masters I purposely moved out of the "crowded leave on top of eachother" lane (also known as the PACK) and donned the paddles to do the faster interval in a less crowded lane.