I guess he design helmets like this beauty

***SPOILER***

Even if all Ozai does is sit on a throne all day, that is enough. The whole reason the fire nation is fighting a war is because the fire lords have told it to do so, basically, the firelord is there to inspire the troops to keep fighting. Without the firelord the fire nation has no more drive, at least not in the direction they have been taking it. Which is why the Avatar needs to defeat the firelord.

Based on that fact that we haven't heard of any major military accomplishments from Ozai, we can assume that he has no particular talent as a general. If so, it is to Ozai's credit that he has thus far managed to restrain himself from interfering in in military matters that he really would be no help in, instead leaving them to talented strategists like Azula and Zhao. History is littered with empires that fell because they were ruled by strategically hopeless dictators who still insisted on trying to win the battles themselves to prevent anyone else from taking the credit. The rulers who succeed are the ones who maintain firm control over their subordinates, but not in a way that will restrain those subordinates from doing their job.

What does Ozai do all day? I'd say that he spends most of his time recieving endless reports about absolutely everything. He knows direction he wants his empire to be heading in, and if he comes across anything in those reports that he sees to be impeding it from going in that direction he focuses his attention on the problem and gives orders for it to be corrected. An example would be the siege of the north pole . Ozai was probably recieving regular reports from Zhao, and so knew that Zhao was taking a massive fleet to the north pole in pursuit of the avatar, Iroh had joined him as a general, and Zuko was still failing to capture the avatar. When Ozai recieved a message from the fire navy about their defeat, he would have thought about what had been wrong with the reports that he had recieved, and concluded that Iroh being there, and Zuko having failed in his task were the main anomalies, and so must have had somthing to do with it. Ozai then ordered Azula to fix the problem by bringing Iroh and Zuko back to the fire nation.

Ozai also doubtless invests a lot of time practicing his firebending, especially since the avatar returned. My guess is that his style of firebending reflects his style of ruling the firenation: he maintains total control over every part of it. He will not know any unique moves of his own, but rather will have completly , mastered every single move, both basic and advanced. The lightning bolt he threw at Zuko was an example of this - generating lightning is not unique to Ozai, but he is better at it than everybody else.

The scene in which Zuko redirected Ozai's lightning back at him, far from being one of Ozai's weak moments, is one of the bigest indicators of how srtong he is. When Zuko redirected his lightning back at him, the bolt did not, as seems to be the opinion of many, simply strike the ground at Ozai's feet, it hit him directly in the chest. That same lightning bolt would have demolished a stone wall, blown apart the side of a cliff, and killed the avatar in the avatar state, but all it did to Ozai was knock him back against the wall, and not even that hard - when he got back up a few seconds later, he didn't even seem to have been winded. It's all the more scary when you consider that Ozai was not expecting this, so it wasn't even some powerful new technique, it was somthing he did purely by instinct.

Ozai has faced accusations of cowardice, but these too were disproved in the DOBS scene. If Ozai was a coward, then once Zuko announced that he was not going to kill Ozai, but instead leave him for the Avatar, he would have just stayed quiet and breathed a sigh of relief at having avoided death. Instead, he mocked Zuko for being a coward, and goaded him into staying around and doing the job. When this didn't work Ozai brought up the subject of Ursa, skillfully manipulating him into staying. Ozai was perfectly willing to risk being hacked apart by by Zuko in order that he could keep him talking until the eclipse was over and he could atomize the brat for daring to defy him. The way Ozai easily manipulated Zuko from preaching about how evil the firenation had become to tearfully demanding to know what had happened to his mother makes it fairly clear who Azula inherited her ability to manipulate people from.

Well, thats the end of my rant about Ozai, hope I contributed somthing to the discussion.