Layman terms Donald...j/k. I think I get what you are saying and it sounds like you are suggesting 2-3 days a week of 30min+ in what I would refer to as my zone 1 heart rate. You are correct when you said that would not feel like I was doing much because I actually do a similar workout for recovery when I am feeling really run down. I rotate between a bike and elliptical for 30 minutes in zone 1 then do some stretching afterwards and that would be all I do for that day. It usually helps a lot with my soreness but I never thought of it as something that would help cardio conditioning.
This is definitly contrary to the Crossfit/Ross Training GPP type work I've been doing to try to increase my cardio. Are you suggesting to just tack this 30minutes at the end of a strength workout or MMA training day?