I found that by changing around my routing a bit, I was able to fall within the MHD fare.
Day 1 YYZ-DFW J
Day 3 DFW-CUN J
Day 5 CUN-MIA J
Day 7 MIA-DCA F
Day 9 DCA-YYZ Y (ERJ-135)
This worked out to $1360 + tx
Y ticket is about $1100 + tx. It's not worth it to purchase Y and then upgrade with AA status because it would require about 9 or 10 upgrade credits to do the whole itinerary. (10 credits = US$312.50 value)