Using that five-fold test, the Watchtower is a cult. You need look no further than their own history and publications.
1. Does the group have a charismatic, strong leader (or leaders)
Yes, Joeseph Franklin Rutherford, esq. being the most prominent. After seizing control via a corporate coup d' etat, he separated the fringe religious group founded by Charles Taze Russell from what little credibility and respectability it had left (after the failed 1914 prophecy).
[2] Does the group squash individuality as well as independent thought?
See Watchtower January 15 1983, page 22, "Avoid Independent Thinking." Here they equate independent thinkers to satan and rebellion against God:
"From the very outset of his rebellion Satan called into question God's way of doing things. He promoted for independent thinking. 'You can decide for yourself what is good and bad,' Satan told Eve. 'You don't have to listen to God. He is not really telling you the truth.' (Genesis 3:1-5) To this day, it has been Satan's subtle design to infect God's people with this type of thinking.--2 Timothy 3:1, 13.
How is such independent thinking manifested? A common way is by questioning the counsel that is provided by God's visible organization..."
So according to Watchtower even posing the question is evil. You don't even have to disagree; the very act of thinking about the issue is rebellion. Against whom? None other than the self-proclaimed "God's organization!" (see question #1 about the leaders). Also see Watchtower May 15 1984, page 15:
"So important is it never to raise the voice in bitter criticism of the Lord's organization or its appointed representatives."
3. Is there a denial of intimacy by excluding or alienating friends or relatives?
The Watchtower organization is proud of their shunning policy. From Watchtower April 15 1988, page 28:
"Even if there were some family matters requiring contact, this certainly would be kept to a minimum, in line with the divine principle: 'Quit mixing in company with anyone called a brother that is a fornicator or a greedy person (or guilty of another gross sin),...not even eating with such a man.'--1 Corinthians 5:11.
Understandably, this may be difficult because of emotional and family ties. such as grandparents' love for their grandchildren. Yet, this is a test of loyalty to God...Anyone who is feeling sadness and pain that the disfellowshipped relative has thus caused may find comfort and be encouraged by the example set by some of Korah's relatives.--Psalm 84:10-12."
The gloss "(or guilty of another gross sin)" and the emphasis is from the original article, not my addition. They admit it is a loyalty test. They don't mention that Jesus himself dined with sinners (see Mark 2:15-17). Finally, Psalm 84 is about the glory of God, not judgement to our neighbors. From New Jerusalem Bible:
"[10] Better one day in your courts than a thousand at my own devices, to stand on the threshold of God's house than to live in the tents of the wicked. [11] For Yahweh God is a rampart and a shield, he gives grace and glory; Yahweh refuses nothing good to those whose life is blameless. [12] Yahweh Sabaoth, blessed is he who trusts in you."
[4]. Do they apply financial pressure and abuse for the welfare of the group, even at the personal expense of the adherent?
Watchtower August 15 1987, page 20 encourages parents to persuade their children to forego normal career goals, so they can pursue unpaid, no-expenses-reimbursed, full time service to the organization:
"So hold forth the goals of pioneering and of missionary and Bethel service. Help them to appreciate that the ministry is a career with a future and that there is no real future in worldly careers."
[5]. Does the group keep its members separated from their surrounding community?
Watchtower August 1 1986, page 14. Note the loaded language: "Satan", "this world", "people of the world."
"Be alert, also, to other designs of Satan. Sports, music, and dancing, for example, have become a prominent part of this world's entertainment. True these things in themselves are not necessarily wrong and can be pleasurable and even beneficial... Satan, however, has deceptively promoted the view that they pose no real threat of harm, even when regularly partciptaed in with people of the world.
Watchtower June 15 1980, page 8 equates non-Witnesses to poisonous snakes:
"Without a doubt, our appreciating just how wicked and corrupt Satan's world is will help us to keep separate from the world. Such appreciation will make it easy for us to obey the command found at Psalm 97:10: "Oh you lovers of Jehovah, hate what is bad.' ... avoiding them as we would poison or a poisonous snake, for they can poison us spiritually."
