HAL connection planner said MCT was 70 mins (it's in small purple letters under the part that displays your flights) BUT if BA are prepared to sell you a ticket with a connection time lower than that then they are taking responsibilty to protect your ticket and rebook you (assuming this is on the same ticket)

Many thousands of people transfer at T3 every day with little issue and often in a lot less time. The MCT is what the airlines and HAL feel is sensible for allowing for baggage transfer and passengers to be at the gate on time etc it is not the expected time it takes for passengers to actually do it.

Your main issue is whether or not AY will allow you to switch. I'm guessing that 'bad reviews' isn't going to be a valid reason!