gedunk:IMO, with a paid DM, your hiring both. Depends entirely on the dive, the divers and the conditions, on how much of one or the other come into play.
Id disagree then - when a book a dive trip for the first few times im happy with a guide so i know the route, what to see and so on (and id expect a good surface briefing etc). However in the water id expect qualified divers to be able to look after themselves, otherwise youd hire an instructor or something
I know that from experience. Most qualified divers i have escorted to the surface would have been fine by themselves. Some needed me or a buddy along to assist in making a safe ascent. It is not always apparent at depth who will have troubles. Thats a major reason for a buddy system in the first place.
Again my solo surface thing im refereeing to maybe 30ft depth, boat and line clearly visible, warm water, no currents and so on and i really cant see a problem there. I wouldnt advocate it in low vis or other conditions. In tropical type waters the surfacing diver can see and be seen by the rest of the group if needed and as qualified they should quite happily be able to manage an ascent on their own - if not why are they diving as qualified? Again its back to the issue of do you want a guide or do you want a babysitter/instructor.
I ask the question again, do you have experience as a DM or group leader or are you basing your opinion only on personal accountability being a good thing?
Ive dived as cattle heard style groups when abroad (not an issue back home as its entirely independent buddy pairs) and have seen divers surface alone, with a buddy, pairs changing underwater and so on. You get to know quickly what to expect and as i said, ive got no problems with being changed underwater, being sent to surface from 30ft in clear sight of the boat and other divers alone nor anything else. Other people ive dived with have also accepted that. (In fact in greece this year i ended up with a regular buddy for 2 weeks and she was heavy on air and suggested quite happily they she'd return without me on running "low". The staff agreed to this - everyone was happy.) I still think that as professional divers you should be able to look after yourself and not have to rely on some guide to keep you out of trouble. If you ARENT capable of doing that you really ought not to be diving at all. Surfacing in clear waters from about 30ft with maybe 6 divers below is hardly solo diving and neither is following a group of 6 or so divers where 1 person has left that group.
Here in the US, if you knowingly send someone to the surface solo and they get hurt, you lose if they sue. Don't even bother carrying insurance to protect yourself. Because it will be worthless. Most policies have the minimum requirement of enforcing the buddy system. Most insurance providers today won't even blink an eye before they drop you. You would most likely be on your own in defending your actions.
If its a breach of guidelines then fair enough you can be sued. That'll be the same for any country. Insurance companies are fast to invalidate at the slightest chance. However if those are the guidelines i disagree with them but thats for a different topic/thread.