My experience from several trips per year via CUN:

We arrive by private transfer/taxi at airport approx 75 mins before departure. There is never more than 3 minute wait in Business Class line. Bags need to be checked 60 minutes minimum before departure in CUN (per my experience).

We usually check bags approx 65-70 mins before departure. Never a problem. Then without delay, get through security etc and head straight to gate.
Saturdays have longest security lines....but also more flight delays.

Never had a problem with this plan for last 6 years and 15-20 departures from CUN on AA to DFW.^