Surely the passage of time flows differently in different panels in a comic, and OotS is no different. Some times, each panel shows long speeches or complete dialogues; other shows a single line (dramatic ones, most of the time). But when showing a combat, each panel often shows a single action or a single round - as well as its immediate result. That's the key word here.
I'm no expert in Architecture and Engeneering, but the demolition of the arena is not not immediate results of Roy's actions. And, even if it was, this scene is more a exception to the point I was trying to make than a good example. If I have to guess, the delayed demolition of the arena serves mainly to create tension, as a form of highlighting the consequences of the previously shown actions. In the other scene, however, Roy is attacking Thog with increasing anger - hence the last attack having both bigger consequence and sound effect.
How do we know that Thog's level is tied to Roy's? Roy pretty much says that's not the case, so I don't think we could use the personal rival rule.
The thing is: Roy is the most all-around competent character in the Order. I find it hard to believe that one low level Fighter could be more competent than other high level classes. And we have seem lots of sittuations in which this rule seems to apply. The arena fights are more important to the actual thread 'cause they are post-resurrection.
He was able to rescue the party all by himself, and solo Miko. He handled both bounty hunters (who have, themselves, defeated half the party) in the bar fight, and was selected as a better warrior than the half-dragon. Let's not forget that he jumped to face Xykon all by himself - being a non-cliche, not-stupid fighter, I figure that he had reasons to believe that he could actually succeed. He was later proven wrong, obviously, but we know him to be competent fighter and a brilliant tactician: implying that Roy tried to deal with Xykon without even the slightest chance of success would be contradictory with which we know about him.
That may be, but I was just pointing out how he could have access to XP. And don't forget about his completed quests and character growth mojo.
But I'm not really all that comfortable trying to justify his XP. We don't know how the whole post-death thing actually works in OotS -it seems to me that it is quite different than 3.5 Rules As Written, but then again, maybe it isn't. But, as people keeps insisting on the "show me some XP source" argument, I keep speculating about it. But knowing, for sure? Impossible. And, as I said before, not really my point.
I'm with FujinAkari in this one. Also, it looks like Roy acknowledge being higher level by saying "With great power comes great blame".