I've had a similar issue in the past. I found the cause was that the email address is case sensitive. iOS was auto-capitalizing the first letter in my email address, which caused it to fail. Fully lower-case worked fine.
I have the same issue. Only 15 items in a feed is pretty low, especially when you have big events like E3, PAX, or the recent Wii U launch. When they dump a bunch of videos up at the same time, my podcast app ends up missing videos, which means I miss videos. Kinda defeats the purpose of RSS.
Why is it dying? The system is just a couple of months old.
It's not dying, but people feel the need to say it's dying in every thread about it. Usually there are also always mentions of how smartphones have killed the market for gaming handhelds, but that's oddly absent from this thread so far.
In the Subscriber RSS feeds, there's an obnoxiously low number of entries. Normally this is irritating, but not a problem as my normal workflow involves checking daily. However, thanks to the sheer output from E3, I missed out on a day's worth of videos in my RSS reader. If you can't permanently increase the number of entries in the RSS feeds, please consider temporarily doing so during big events that cause you to generate a ton of videos (e.g. E3, TGS, other conferences).