I'm at work and frankly not massively invested in this debate so I'll be brief.
1) Saying Marco is an example of stamina drain isn't true. Saying he's possibly an example of stamina drain is, it could be that he has a regeneration limit regardless of his stamina, whether he's drained or charged like the Energiser bunny. Other characters have shown limitations that don't appear to be stamina related like Bartolomeo and his barriers, or Buggy not being able to levitate his feet, or Foxy's beam's effects only lasting thirty seconds.
I didn't say Marco's Devil Fruit is an example of stamina drain. I said it might be. What I'm saying in my previous post is that there's no reason for you to treat him as an exception, if his ability is tied to stamina drain or has some "phoenix energy" that runs out.
2) Yes I'm arguing based on an absence of evidence in the sense that nobody has outright come out and said my DF doesn't drain my stamina, but I feel that, that is still the stronger side as Oda appears to have called out Law and CC for having stamina drain in what appears to be an exception basis.
I've already explained why I don't think absence of evidence is evidence of absence in this case. I'm not sure how to respond to this when you insist that your interpretation of it is still the stronger argument, because I've already objected to your reasoning and you're not addressing my objections.
There have been countless opportunities to explain that DFs drain your stamina, none have been taken, and this is a fairly big point to just bypass.
How big a point is it? Fights in OP rarely have stamina as a major deciding factor. (The only one I can remember off the top of my head is Rayleigh's fight with Kizaru.) I don't think it's comparable to intangibility and haki, because those are always among the most significant issues - if not the most significant - when someone fights a logia. And Petite has already adequately addressed this, in my opinion.
Weaknesses of the DFs have been expanded on quite a few times (superiority, exploiting the element, Haki, water, salt, seastone)
And how many of these were explained before they started to matter? And how were they explained? Oda works by implication. We know elements can be exploited from three cases (Crocodile, Eneru and Monet). Oda didn't tell us the rules. He showed using a small number of examples. We know of "superiority" from one case (Ace vs Akainu), though I don't think I need to point out that we don't know how that relationship works (because it wasn't really explained). Now, we have two cases in which two Devil Fruit users have explicitly mentioned stamina issues. While not conclusive, I don't find anything inconsistent in the way things are explained, because Oda hands things to us piece by piece, over time.
Additionally, there is no reason whatsoever to give Caesar and only Caesar a finite amount "gas energy". That's one point you haven't addressed. Why Caesar, if not to imply a general rule about logias? How does his limit serve the story? What is the point of it? If I remember correctly, Caesar didn't show signs of tiredness when fighting Luffy, but extensive use of Gastille on the bridge in Dressrosa made him pant and then complain later.
In order to argue that your side is stronger, you need to at least indicate that it isn't likely that other fights are analogous to the Caesar case, that it isn't likely that DF users weren't actually taxed by the use of their abilities. You need to argue that [absence of evidence = absence of stamina drain] is more likely than [absence of evidence = no fights with stamina issues], even if you exclude Caesar and Law from the pool of evidence. In other words, is [Enel can produce an unlimited quantity of electricity] more probable than [the amount he produced so far didn't drain a significant portion of his stamina]. That's when absence of evidence becomes evidence of absence.
Edited by Tale, 22 October 2014 - 12:07 PM.