You are microwaving it too long. Reduce the time to 3 minutes, and do only 1 ear at a time. I cut the ends off first before cooking. Then after it cooks you have less "hot" to deal with. The 3 minute cook will make it more crispy and not so mushy.
Another technique is to husk the cob completely, then wrap in a soaking wet paper towel for 3 minutes. I prefer to leave the husks on while cooking though.
I've been doing the microwave corn on the cob with husks on for years and years now. I even take ears of corn with me to work and fix it in the microwave there. (my company has a cafeteria), so when I pull out the steaming hot corn on the cob, everyone around me always asks, "Were they serving THAT today? I didn't see that! Looks wonderful!"