I had a short layover (45 min) in Charlotte recently. Everything had to align perfectly for me to make the connection.. it didn't. My plane didn't leave on time, was delayed due to some weight issue. We were in line for take off then removed. Then we had to get back in line. All this took 45 min, which ate up my connection time. The plane actually made up time in the air and we got in 15 min late. The plane still had to taxi to the gate which took another 10 min. My connection gate was only 2 gates away, but still had to deplane, which took 20 min. Thankfully, the connecting flight ended up being delayed an hour.
In short, you never know if you're going to have the "perfect flight" to get you to your destination on time. Too many variables not within your control at play. I would say 30 min is too close to try and make a connection.