I have only encountered one bot that I have found useful: @trufflepig they promote posts that seem to be decent but not enough to be on the trending page. I have found two blogs I now follow through that service. 

I do otherwise abhor bots. Voting bots are a joke, it’s taking the whole concept of this platform away from the way it was intended. This is supposed to be about people creating content, others reading it and the reading validates the design; if someone likes the content they give it an up vote, if they dislike it they can not vote it, flag it(which I think is ridiculous but that’s another discussion) and comment. The engagement this process brings brings a level of interaction that’s not found at such at level elsewhere. But of course the bots have changed that game completely. It’s difficult to even get recognition by posting unless you go to other blogs and engage with as many people as possible without these bidbots. 
There needs to be a cultural shift on the platform but a shift away from these bots is unlikely since there are heavy hitters that are invested deeply in the continued success of the bots.