My reasoning for having a blog/website is not so much to earn revenue from it, but it's to ensure that Google indexes the videos. Yes Google displays related videos in a google search, but those places are filled by top ranking channels, and we all know how hard it is to get to page 1 of Google.
If you have a page/post on your own domain name for every video you upload, and that page has a detailed description of the video (you can use your YT description, but change it around a little as Google hates duplicate content), that is much more long tailed keywords and all sorts of variations for Google to reference. So there's much more chance of your blog coming up as a result in search, even if not in the video section, then in the page section.
I also have Adsense on every page of the blog. I don't expect any revenue. But what it does is force the spider to regularly crawl the page to ensure the ads are relevant to what's on the page. If you don't have Adsense, it's much harder to get the google spider to crawl every page. (Little trick form my old internet marketing days with google sniper sites).
Your other question - when to use Adsense? You need to consider it in terms of your overall marketing strategy. What is your marketing plan? Do you have a marketing budget?[DOUBLEPOST=1470227055,1470226581][/DOUBLEPOST]
Ye those suggested slots are the holy grail. I'm no closer to figuring out how to get in there. Although I am adopting a targeting strategy will see if it works. There's a certain component of randomness to it (perhaps what seems like randomness is the algo giving all channels a chance). The algo rotates videos in and out, but it definitely seems you have to be in an authority tier to get a slot. We've only ever had 1 RTR slot for that 1 day, but we have had many slots in 200k-500k channels, and only 2-3 slots in 1m+ channels.