You do not need whales or followers, just put your own money and have your post raise in the "hot" or even the "Trending" list.
That will only be an indirect effect though. The actual post will only move up in the Promoted section as a result of the payment. To demonstrate I have promoted your post.
Agreed. It is a short term push only. On the long run, recurrent post-quality and powerful followers are key.
Do you know if promoted articles also feature in the "trending" list (upon massive promotion at $ X00 levels) ?
Only if they make enough money by people voting on them. Right now the promotion does not change the actual value of the post - it just gives a ranking and position on the Promotion page. If by being on their enough people vote on it then in theory it could indirectly put the post onto the Trending page.