Are international standards the same as US standards? I honestly don't know.
What are standards in the US? There may be some relatively common industry practices in the US, and similarities across training agencies, but even then if you dig in standards may not be as standard as you'd think.
The problem was that unexpectedly, someone I felt responsible for was on 50 bar. How could I plan for that?
Setting aside all fault and responsibility, and merely focusing on what YOU can do. During a SCUBA accident/incident it's usually important that you make a safetly-oriented decision and act on it, even if that decision is an imperfect decision. We may be nacred, in an unfamiliar environment, dark, cold, covered in restrictive scuba gear, limited vis, and acting based on limited and imperfect information. But
the important thing is to act.
You mention planning which implies what can you do before the incident occurs?
- The majority of incidents that become accidents seem to follow a "3 strikes your out" pattern. Unexpected things happen during dives. However, as scuba-divers, we plan for the unexpected typically by having redundancy of some sort.
- Divers normally "plan" to be have enough air to ascend while also sharing air with an OOA diver. Or when solo, one usually has a redundant air-source (also good for non-solo).
- The dive-op should have had a dive briefing about what divers are supposed to do when separated from the group. Without any specific pre-dive briefing, I'd generally assume you just surface (or DSMB and surface).
#3 being the interesting one. You might have to be more mindful of red flags going forward.
"What, we're diving in a current and doing a wreck penetration, but there's no detailed safety briefing?" Regardless of who is at fault, or who is to blame, I want to be 100% (or 99.999...%) sure I'm coming back from every dive alive and well.
For example, this is why I bring a redundant air-source on EVERY dive, regardless of depth or the number of available dive buddies. Even if I'm an idiot who forgot to monitor air (strike 1) while my insta-buddy swam off to look at a lobster (strike 2), that's still only a mild annoyance because I'll just have to surface early.
some of you agree that this is perhaps more dangerous than I previously realised, yet it doesn't seem like I had a better option given the circumstance
If it was dangerous to simply surface as you did, it's a huge problem that the dive op didn't tell you that.
when we booked the liveaboard I assumed they'd have a dedicated instructor or do their training dives separately from the rest of the group. He was put on a position where he had to either tell my friends to skip several of the dives on the trip, or tell the rest of us ro be unguided
It's a terrible experience for both (1) the students, because the instructor isn't focused on them and (2) the normal customers expecting a guide. To me the idea of someone instructing and guiding on the same dive is a gigantic red-flag with flashing lights and a siren attached.
Realistically, only one of those jobs can be done at once, and trying to do both equally, would just mean doing both poorly. Was he doing drills with the students during the dives, making everyone else wait? Did he not do any drills or skill practice during the dives? From the student perspective, these dives are supposed to be pushing divers to new limits at the edge of their skills.