Yep, I agree with Schwann on this one - with separate tickets the QR IT would have had no way to assess that a late arrival would mean they are under MCT and proactively cancel the onward sector.

Assuming the OP can do OLCI for the DXB flight they just need to get to Gate before it closes as Qatar will check any bags through if asked at the origin - as to see the check in supervisor if there is any query or pushback.

If the flight arrives on time into Doha 1h30 is fine, but 1h or less will start to get tight, especially as the OP will be taking the risk that if they fail to get to the gate Qatar do not need to offer the OP any protection or rebooking (but they might do as a customer service gesture if it was their own flight that delayed their arrival, there are some past examples, but don't depend on it)