I fly to/through there at least once a month and have never had a carry on weighed checking in or transiting through DXB (I am gold so check in at J desks even when flying Y). My last flight in J I had a full backpack a large purse and a large dress garment bag and had no issues.

As others have said- if it looks like you are struggling with it, they may ask to weigh it...if you treat it like it is light they will probably let it go.