Yes, taking DNG is enough, because the other three ter are already ANZAC.
I have played five games so far. Three times the allies won and twice Japan. I agree with the comment that the allies come back later in the game. I think one of the strategies you could use is giving multiple targets. The three bombers on the three island with an AB is a good example. Japan can only take one and it will give him logistical headaches. Because the tran he uses needs protection, and stuff like that.
Yesterday I won as the allies while I was getting my ass kicked in the first 10 rounds, or something. India had fallen and Japans naval force was extremely large. I did a very daring move to the Japanese coast and took Korea and Manchuria. I put two destroyers in the seazones to block of the big Japanese fleet, so I could hold Korea for another turn. He wasn’t able to get it back and I build a minor IC on it and landed every single plane that could reach it, thus sacrificing my fleet. Elsewhere I attacked a smaller Japanese fleet with three trannies in it with my ANZAC subs and planes.
I build three tanks in Korea and upgraded it to a major IC. He lacked trannies so he could only land 4 land units and get all his planes in action. But with the captured AA (Manchuria) I had a force of about 7 land units, an AA and about 10 planes. He lost that battle and in the mean time ANZAC was capturing DEI and China was recapturing the Burma. China still lived while they were once only two ter left. But with some luck and my fig intact and with the help of Manchurian IPC they could reclaim their lands steadily.
Japan gave up and the allies won their third victory. So I think to state that Japan is overpowered is a bit exagerated. You can gain a lot of ter and income fast, but to keep a hold on them while the US is growing and the other three (or in this case two) are harassing you with small skirmishes and a lot of ANZAC subs to kill lone ships and raid vonvoy boxes, that’s the difficulty!