What you have decided to do on DTube is very noble!

I've also noticed that some users dominate some of the services.

Did you notice this one on dMania? - https://steemit.com/dmania/@artz/dmania-2017-statistics

Here are the stats for 5.5 Top authors by comments under their posts"

And here.. top authors but number of posts:

Looks like some of guys are addicted to dMania. I see one with 15% which is super impressive indeed.

I think this is basically a good illustration of what you are saying.