Are you checking in any luggage? This one bit is quite detrimental, as luggage may take forever to arrive on certain days, regardless whether you have priority or not.

Depending on the day, there can be quite a backlog at immigration, which could further delay your transfer process. Note that a Qatar flight arrives at 07:45am, which may affect how busy immigration will be.

The skytrain takes around 5 minutes to go from T2 to T3, though getting to the station itself is quite the hassle, so 20-40 minutes (depending on luggage/mobility) for the whole ride would make much sense in my experience. Then there is the 1 hour check-in cut-out...

I mean 2.5 hours is doable under certain circumstances (hand-carry only, holding Indonesian passport/residency) but shouldn't be attempted in other circumstances. YMMV really...