It's hard to say where the line is between getting your post a little more interest in the feed of your followers (due to showing them rewards they can get a piece of) vs. gaming the rewards system. I think there is a line though.
This is the key! Where is the line the community should be comfortable with. When it is all said and done, all of these promoted posts, take from the rewards pool. The pool does not change in size, so some other posts are simply not getting as much attention.
I use the bots as well, there is at this point very little chance a post can get attention without these bots, this is heroin addiction we are all on.
Blessings