how to decide if a blog is worth buying an article/backlink on

I get most of my link power these days from pbns but I also buy articles with BL on good topic related blogs from time to time to get a better diversification. I made a lot of mistaked in the past as for example buying posts on sites which were penguin penalized before, had a spammy backlink profile etc.

I want to discuss here which criteria you use to decide if a blog is worth buying an article on.

I use these:

• PA,DA > 30, CF,TF > 20. PR => 2.
• good backlink profile with mostly branded anchor text
• overall feel of the site, should not feel too much seo-ish
• this is an important point which I missed in the past: Does this site actually rank for its keywords? Yesterday I found a seemingly good site in my niche which fulfils the criteria above but I found then that it does not actually rank for mildly competitive keywords. If the topic of the site is health and there is a blogpost about "Recep technique for professional teeth cleaning" I expect this post to rank for "Recep professional teeth cleaning" unless of course it is a really tough kw. Sounds obvious but I bet a lot of guys looking for backlink partners do not check that.

Whats your opinion, any more things I should look after?