Let me answer the question posed in your post headline - How dangerous? There is no way of knowing what goes on in other's minds so your question is unanswerable. However, let me make a few observations as one who has crossed the North Atlantic twice - single handing once and with a crew the second time. (Remember that the North Atlantic goes all the way down to the equator - so crossing from the Canaries to the Caribbean is "crossing the North Atlantic.")
Let me first distinguish between "danger" and being unprepared. Loss of a boat and/or crew that does not have proper equipment properly maintained has little to do with the location other than the proximity of rescue services. When (not if) things break there has to be the ability to recover. Hopefully on a well prepared boat only a few things will break and one is able to overcome - not so much on an ill prepared boat.
"Danger" on the other hand is somewhat random. I crossed the Atlantic eastbound (in other words at the higher latitudes) during the "preferred" weather window of June/July. Almost the entire trip I was hugging the south boundary of the route while a succession of gales and one unseasonable and unusual mid-ocean hurricane passed to the north. I had daily or twice daily contact with shore based weather routers who kept me out of the worst of it. I still had to deal with 45 knot winds and scary seas. In another year or perhaps another month the trip might have been a cakewalk. Given that it took (including stops at Bermuda and Azores) 44 days from Florida to Portugal no long range weather forecast was going to help me. My point again is that how the weather is going to develop over a long passage is quite random.
I have read my fair share of vessel lost stories and the common factors in all are either weather or stupidity - sometimes both. I was in Miquelon Island. Next to me was a couple that had cruised for many years. One morning I noticed that they were getting ready to get underway. Since we had been stuck in Miquelon for several weeks waiting for a weather window I immediately went down and checked the weather forecast. It was for 45 knot winds and 15 to 20 foot seas in the Cabot Strait. They set off for Sidney, NS. I figured that with all of their experience they might know something I did not so I set sail for Halifax. Within a hour I knew I was in serious trouble so abandoned the attempt. Unfortunately going back into Miquelon was not something I wanted to do so I just headed south toward better weather. (I am here so you know I survived.) A few weeks later I got an email from the couple. It said "when we were in the Cabot Strait we had 45 know winds and 20 to 25 foot seas. They ripped the dinghy off the transom, caused significant damage to the transom, shredded the mainsail and the jib, and caused significant additional damage to the standing rigging." Not surprising - after all that is exactly what the weather forecast predicted.
You are welcome to lobby for a "boats lost thread." I suggest you have subforums for weather, stupidity, and weather and stupidity. I for one would not find such a thread particularly useful.
Fair winds and following seas