I'm not really sure what the actual point of this type of thread is.
Obviously 30 minutes is in fact doable or else Delta wouldn't sell this ticket. They aren't going to set the MCT so low that you'll actually misconnect on a regular basis, since it's expensive for them to handle misconnects.
On the other hand, clearly no connection time is sufficient to absolutely guaranteed a connection is going to be successful.
I understand the point of the thread more than I understand the point (or lack there of) in your post except to be unnecessarily condescending from the comfort of being behind your computer monitor (par for the course for you on this forum though). If you don’t see a point in a thread, don’t open it and respond. Seems simple enough, no?
Anyway, [MENTION=14649]david55[/MENTION], my vote would be for DTW. As I mentioned above (and SJC ORD LDR noted as well), by connecting in DTW you’re close enough to be able to easily drive to CLE if you get to DTW and misconnect. DTW also has service to CAK not too far down the road as an alternate option, depending on where you’re going in the Cleveland area once you arrive. MSP does not have service to CAK.
One additional note: since thus trip is for June there’s a good chance it will be impacted by schedule changes and adjustments which could either lengthen your layover a bit or it could drop your layover below MCT and thus give you a free reroute/rebooking.