I have seen legibility is often sacrificed in behalf of... a casual writing style? At least I have found a dozen of long posts around here with no line breaks, punctuation and not even proper use of lower and uppercase such as "i live in the usa and, dont understand your point"
I agree that 350 to 500 words is a sufficient. Sometimes you can go a little bit longer, but you'd better make it interesting.
I generally try to write exactly like you said. Plus some pictures and video. Hit em early, hit em often is my motto. Try to shock/humour/interest right off the first sentence and keep building.
Every time I'm having the feeling an author is in hurry to sell his/her goods when I read a short article. My opinion is, ones less 1000 words should be called NOTES, not articles.
If you write an article of 500 or more words it will acceptable to all the directories which includes isnare.
Try to shoot for an article of about 400 - 500 words. That makes it long enough to be of interest and worthy of a read but also short enough to not scare off anyone who scrolled down the page before they started reading. If you're consistently producing longer articles, maybe 800 - 1200 words for example, you should start to think about whether you can serialise it. Getting two or more articles out of one can clearly give you more to publish with the associated link benefits multiplied.
For me, it depends upon the topic and medium. Obviously, if you are writing on a complicated topic, then you are going to need more background. If it's something meant to be short and informative, then you can get right to the point.