This is a very good point. Not all witnesses are well known and some of them make amazing work. I would suggest that to add the following witnesses to your existing list, which in my eyes do a lot for the community:

• steempeak for running steempeak
• yabapmatt co-founder of steemmonsters and co-creator of keychain
• blockbrothers this is @exyle who for example run the interview with
  @andrarchy that helped us all calm down a bit
• arcange who brings daily statistics about the steem ecosystem
• emrebeyler who developped dpoll and other tools
• aggroed for running steemmonsters and steem-engine
• therealwolf because he tends to upvote our community (he developped many tools for witnesses)

There are others but I think it is important to choose witnesses that we actually know and hear from on the blockchain.