My May return flight BRU-DOH-BKK also got a shortened transit change to 45 minutes. I rather preferred the 2 to 2.5h previous transits I had with Al Mourjan lounge visit.
What worries me in case of mis-connection are the fresh foods in my luggage and the domestic ticket on Thai Smile. I will book an expensive J ticket (thank you QR) which allows change of schedule at least 4h in advance.
I have 6 DOH transits booked:
1 45 min
1 50 min
1 60 min
1 75 min
2 120+min
I can miss the extra stress, will see how it all goes, not booking anything in the coming 6 months at least