The transformer does not dissipate 30V x 2A= 60W, or I squared R. Instead it provides 30V at 2A and its efficiency is high so it dissipates maybe only 6W.
A power supply usually has a DC output so for a 30VDC/2A power supply the transformer must be about 28VAC that has a peak voltage of 28V x 1.414= 39.6V. The rectifier bridge has a 2V voltage drop and dissipates about 2V x 2A= 4W. The output power transistors and current-detecting resistor have a voltage drop of about 7.6V and dissipate about 7.6V x 2A= 15.2W.
Since the 39.6V peak voltage of the transformer must provide 2A then the transformer should have a power rating of 39.6V x 2A= 79.2VA, not 30V x 2A= 60VA. The 28V transformer must have a current rating of 2A x 1.414= 2.83A.