You should never hand over your safety responsibilities to another.
Dives don't always go as planned.
Small differences in profile can matter (depth, time, surface interval, ascent rates).
If something bad happens, you (not someone else) pays the price.
Agreed on all points.
However...
Sometimes you shouldn't bend certain rules, sometimes I feel its the same as a LDS telling you to service your reg every year giving you the run of the mill excuse "because your life depends on it".
Yeah if you dive everyday, go ahead and service it more than once a year. If you do 30 dives a year and rinse your reg well, don't bother servicing it for a couple of years. Thats what I think. Shrug.
Same thing with the DC. You're doing repetitive dives everyday for a week, then have your own DC or use tables and be more conservative than what they say you need to be. You're doing tech and deco, nuff said. You're doing shallow dives of less than 20m and only 2 dives on this particular trip, then I think you can stretch the one diver one DC rule a little bit, provided the diver skills are good enough to stay close enough and the conditions are very favourable.
New divers? Use the tables. But even so, new divers rarely have the buoyancy required not to have a see sawing profile, so even if they use tables to plan, the dive may not go according to plan.
If all the conditions are favourable and divers are skilled enough and there is only one DC (ridiculously rare scenario) keep the diver with the DC a few feet below and all the other divers stay at his depth or slightly above. The DC becomes a more accurate version of the tables by calculating your profile more efficiently.
Don't get me wrong please, I'm not recommending it. Just saying chances are, its not going to be the last thing you do provided you keep the basics in mind.
For those who don't keep the basics in mind, no DC/tables/instructor can keep them alive no matter how many of them there are and how good they might be.