Here is Alside's Techcenter website where you can see most of the data on the Excalibur and any other line.http://www.alsidewindows.net/Companies/Alside/al_index.htm
You will want to look up structural data to see air performance numbers. They actually list their window at a 0.21 cf/min at 25 mph.
The mil thickness of the extrusions (0.071) is not out of industry norms. There is no industry standard. The Excalibur has a very thin profile and requires probably more reinforcement and engineering than is currently in the window. That is not the Excalibur's mission and/or price point. The window is not going to collapse on itself nor is it class leading with its design pressure rating. It is not aiming to do so either. It is a decent entry level window with more than a few competitors that I think are better candidates in the $400-500 range.
AAMA and Keystone are the two large laboratories that independently certify structural data (air/water infiltration and design/structural pressure).
I wouldn't know where to send you to for seal failure data. The Window and Door Magazine might be a good starting point. As I prefaced, the high incidence of seal failure is just my personal experience in comparison with other windows. Certainly no one is perfect and perhaps it is just bad timing, but there seem to be quite a few remakes coming in of late.
There is no data to my knowledge to indicate that seal failure rates differ between Intercept and Super Spacer. If you ask either of those camps, you will get different answers. Preparation is the key to any spacer system and I am not sure if Alside is making their own IGU (Insulated Glass Units). If they are, that would explain dissimilar rates of failure between their products and other privately manufactured (Cardinal, Guardian, PPG, etc other glass manufacturers) products.
I also think that the design of the window can certainly play a role in seal failure. I window that expands and contracts (depending on the reinforcement and structure in the extrusion) will place more sheer stress on the IGU and increase its likelihood of failure.
Triple glazing is probably the glaring missing component. A window that does not have an option for triple glazing while other windows in the same manufacturers line do speaks to the structure of a window in my opinion.
The aesthetics on the Excalibur are pretty plain jane but again that is subjective.
Please let me reiterate that I am not slamming the Excalibur. There is only one poster that I know of on here, who I think was banned, that was very anti-Excalibur. The Excalibur is a price point window and will certainly fill and opening. Are there better windows, certainly. Are there plenty of windows in the same price bracket that Excaliburs typically fall that are better, sure. Is it wise to put a window that leaks that much air into and opening when you are trying to combat energy losses, probably not.