Hive account@transcript-junky, You have the perfect understanding about blogging. People's attention span is usually about 20 minutes after which you tend to loose them. translating that to blogging, a blog with 750 to 1500 words ( max 2000 words) is ideal to retain the attention span, interjected with some nice images and some light conversations.
A serious / dry subject tends to lose attention much faster, so some trivias, titbits, did you knows, short stories, jokes, one liners, catch phrases etc do help in creating an engaging conversation with the reader while keeping the essence of the blog in tact and delivering what it was intended to do.

I am a free flow writer ( first time blogger at steemit, never blogged earlier) I write as the thought comes to my mind and I do not prepare a draft. when it comes to serious subjects or something that needs deeper understanding or research, I read as much as possible first and then spend some time pondering over it and then just start writing as my mind flows. some new ideas and thoughts come in and the blog takes a different path. as you said it is an art that requires constant tweaking.
from your reply I see that you already have what it takes to become successful in this platform. Ciao.