Surely Hebrews 12 : 11 is talking about God's discipline, not man's.
If you look at the entire immediate context (Heb 12:1-13) it shows that it is talking about opposition or persecution that God allows as a form of discipline or training.
First, it shows how Jesus faced opposition. (Heb 12:1-3)
Next, the writer tells the reader that they haven't yet shed their blood over opposition like Jesus did (an obvious point, seeing how the reader is still alive). (Heb 12:4)
Verses 5 thru 8 then make the comparison of a son (the reader) with a father (God) who administers the discipline for the long term benefit of the son. And if the father didn't give discipline it would seem that the father was acting as if the son was illegitimate or not his own son.
Verses 9 and 10 continues the father-son example by comparing God's discipline with the imperfect discipline we may have received from our human fathers. We accepted that, therefore, if we consider God as our father, we should also accept the discipline from God, which, as the context is discussing, is opposition to being a disciple of Jesus. (Heb 12:2)
Verses 11 thru 13 then offer encouragement to allow the discipline to make the reader a better Christian.
The WT is taking these verses out of context when they apply them to DFing. And from what I have seen, they only apply these verses to discipline within the congregation, not to outside opposition. It serves as a good example of WT twisting the scriptures to their own use. They are teaching "the commands of men as doctrine."