I've never understood the meaning of the word "slave" in this context. A slave, to me, is far removed from a servant, who is often employed. A slave, on the other hand, is born into bondage and has no choice as to what his future may entail. Some of these terms, like "discreet slave" are laughable. In fact, the scriptures used by the Witnesses not only is a joke among scholars, but its bland text lacks beauty and elegance.
Why does the WBTS even use the term "slave" in the first place? And what is a "discreet slave"? Someone who doesn't talk out of turn?
In the book of John, we learn that people can progress beyond servants to friends. "Henceforth I call you not servants; for the servant knoweth not what his lord doeth: but I have called you friends; for all things that I have heard of my Father I have made known unto you." This group isn't a class, but is inclusive of all people who come unto the Lord in righteousness and truth.
The Lord states: "Who then is a faithful and wise servant, whom his lord hath made ruler over his household, to give them meat in due season? Blessed is that servant, whom his lord when he cometh shall find so doing. Verily I say unto you, That he shall make him ruler over all his goods." But these are not self-appointed people who give meat unto the people, but authorized and anointed servants. "For ye hath not chosen me," the Lord said, "but I have chosen you and ordained you."
Who has anointed the leadership of the WBTS? Anointing is a specific ordinance that includes consecrated oil; it is not metaphor. And ordaining is the laying on of hands to confer power and authority. The JW leadership has neither been anointed or ordained, but have taken this honor unto themselves. The scripture from Matthew 24 doesn't say that the faithful on Earth who recognize that their Lord is gone and who seize the moment and feed meat to the rest of the Lord's "slaves" are blessed, but only those whom the Lord hath made ruler over His Household. According to the Witness leadership, none has received either revelation or visitation from God or His Holy Angels, so how would they know they are the ruling class? And how would they escape judgment when they appear before Him in judgment and say, "Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works?" Certainly the JW leadership has repeatedly prophesied of Armegeddon, have worked to cast out demons and done many wonderful works. But they're still self appointed, and they've been wrong repeatedly and they certainly have not (as far as I know) been appointed by God to do anything.