I've found this analysis of Mo Farah useful for thinking about how to move. He has midfoot landing but heel contact triggers glute - the running powerhouse muscle.
Interesting. I keep thinking of trying to get some gait analysis. I don't do much core at the moment, it got lost somewhere in the endless list of physio exercises for one injury or another... Interesting about the glutes, have been feeling like I'm running better since doing more glute focussed exercises (including rowing) although it's always hard to know.