Look at the reports I posted on page one: all those JWs were killed while in a group, on their way to an assembly or meeting. In fact, the 27 JWs killed in the Philipines were killed in a Kingdom Hall...told to go to the meeting by the GB during a typhoon.
When the literature says that the Witnesses are protected as a group, it doesn't mean "group" as in "a few people gathered in one place" but rather "as a class".
*** w08 8/15 p. 5 par. 10 Jehovah Will Not Leave His Loyal Ones ***
Moreover, Psalm 116:15 assures us: “Precious in the eyes of Jehovah is the death of his loyal ones.” Jehovah’s servants are so precious to him that he will not allow them to perish as a group.
*** w75 6/15 p. 377 par. 10 Looking to the Future with Confidence ***
Should we expect, moreover, that because Jehovah is on our side he will miraculously intervene to protect each one of us personally from death or injury during the “great tribulation”? Both Psalm 91:7-12 and Proverbs 3:25, 26 have been mistakenly cited by some as supporting this view. The psalm says: “A thousand will fall at your very side and ten thousand at your right hand; to you it will not come near.” Lest we read into this text more than it states, we must ask ourselves if Moses is here talking about the coming “great tribulation” and is declaring a blanket protection for individual servants of God then. This would hardly be so when we remember that centuries later Paul showed that up to his time the devoted followers of Jehovah had undergone mockings, scourgings, prisons, tribulations and many other persecutions, even violent death. However, we can be assured that, as a group, Jehovah will protect them from being exterminated by their enemies during the “great tribulation,” and He, himself, will not touch them during his executing of adverse judgments.—Heb. 11:36-38. [emphasis theirs, though it was originally in italics]
And chapter 7 of the Draw Close book covers this thoroughly, but I won't copy-paste the whole chapter here. The point is, if JWs have some sort of personal superstitious belief that they are protected by the angels, then it didn't come from the literature.
At every assembly (and many meetings) I've ever gone to, the brother giving the never fails to ask Jehovah to protect the attendees as they "return to their various homes".
Well, that may be, but I don't think they're supposed to. It's probably just one of those bad habits that spreads around but isn't approved of, like when brothers had to be reminded not to ask for "extra" holy spirit in the public prayers.
How foolish would the Society have to be in order to claim that bad things wouldn't happen to JWs while in service or traveling to assemblies? Even they're not that stupid.