I agree with you about transparency. I mentioned this to @heimindanger on Discord yesterday and it was then that he added it to the FAQ.
It's not just DTube though. Almost all the Apps on Steemit do not disclose in an obvious place that they take a percentage of the rewards. I mentioned the same thing to the Steepshot developers and they replied that they will add it in their next update.
We as users shouldn't have to sift through posts that are months old to find this information.
Dlive does not take any amount so they are off the hook.
Bravo to @heimindanger for listening to the Steemians! There is nothing wrong with them doing it but the information just needs to be out there for us. I use bots and had I known about this, I would not have boosted any Dtube posts. My rewards were getting hammered and I thought I was going crazy lol