I feel it is relevant to share in this thread my recent (December) experience, where reliance on a dive guide could have ended far worse than it did.
It was in the middle of a weeklong liveaboard trip in Egypt, by that time there was an established rapport and trust between a group of 8 divers and a dive guide. We were doing the first in a series of 3 dives on the wreck of the "SS Thistlegorm". Conditions were bad, it was beginning to get dark, and there was a strong current from south to north, i.e. from the stern to the bow, opposite to what it typically is there. The dive site was new to all except 1, maybe 2 divers in the group.
In the briefing, the guide explicitly said it would be a no-penetration dive, due to conditions and the fact that we were going to do a dedicated penetration dive of the cargo holds the next day. We tied at the stern, proceeded towards the bow, with the current. My dive buddy and I were 2nd or 3d pair behind the guide. Pretty soon, before reaching the bow, the guide stops, gives/receives and OK signal from all, then penetrates the wreck, in the area, as I later learned, of the captains quarters and I guess the bridge.
We swam inside the wreck following the diver in front for maybe 10 min. Upon exiting, the first thing I see is the dive guide and a 2-3 of divers, including my dive buddy, starting to swim away from the superstructure, over the debris field amidships, while ascending at an angle. I follow. A couple of minutes later I'm in a complete blue water, the wreck is no longer visible, I can barely keep up with the group kicking against strong current in my short travel fins. Since we are ascending gradually, have to pay constant attention to the depth gauge.
Another 3 or so min later I don't see anyone or anything anymore, trying to follow the direction we were going, while kicking at full force. Pressure is about 1000psi, maybe a bit more, I'm overconsuming. A few minutes later I'm fully considering deploying an SMB and doing a drifting safety stop, where finally I see the anchor line with about 10 divers on it, blowing like flags, horizontally, in the current.
All is well that ends well. When I questioned the guide on what happened, he said one of the divers became low on air, and they had to bolt to the anchor line without communicating with the rest of the group. We never found out if there was indeed a diver that signaled him that.
Now, there are some extenuating circumstances, of course. For one, it's an advanced dive site, and everyone going there are expected to have experience and a degree of self-reliance. Also, our dive group was considered the most advanced out of the 3 groups on the trip, we always enjoyed longer and more demanding dives than the other 2 groups, and perhaps the guide would not have done what he'd done knowing that there are less experienced people in the group. But, the whole thing brought me at the edge of my comfort zone, which very rarely happens. I can see how this situation could have resulted in at least some people from the group not reaching the line and being blown away in the dusk.