Anyway, to answer you (finally), I think the best case for Sentinel was made by Blair over in Alan's respect thread. It includes the often-heralded "Book-Writing" feat, which is planetary in scope. But there's lots more. It should also be noted that his wood weakness is gone as Sentinel.
I don't know if it ends up equaling Trans. I suppose a case could be made either way. Some of his "most experienced GL ever" or "one of the most powerful men in the universe" stuff is just words. But a fair amount is shown too. Stuff like single-handedly powering a futuristic city-world for an indefinite amount of time lends credibility to him having more power than any but the best heralds and many Trans. characters. And he's got some shockingly good speed feats too. I never got around to scanning in the few additions I'd be able to make to his thread, but it's nothing mroe impressive than what is shown.
You may have perused all of that, but if you haven't I'd encourage you to. I personally think we're dealing with someone who is straddling the line between the two tiers. I won't vote because of that, but your objections to him being Trans. aren't unfounded.
I also dislike the "vs. threads to determine a tier." Too much misinformation and flippant opinions that aren't grounded in a more analytical approach. Not always bad, but seldom entirely reliable.