I agree with you that tech diving can be safe and fun, but it is also possible for things to go wrong with deadly consequences. All I can say is that when I was doing technical diving you were always told that self-rescue was the first option. If your buddy and/or team can help you out then that was great, but we never dove with the assumption that our buddy or team would be able or available to help out. This means complete redundancy and ability to isolate failed components of your life-support system. It is not about solo diving, it is about sometimes being in a place where the only person you can truly count on is yourself.
The dive computers available today are simply not useful.
This is something I strongly disagree with. Dive computers are very, very useful. They can't measure bubble or various saturation levels of different tissue types, but neither can you. The models they use may be idealized and only have a fixed number of compartments for the offgassing calculations, but they provide several other benefits that make them a key component of any deep dive. For starters they track your depth over time. Everyone drifts and bounced around within a range of depths even when you think you are staying on a fixed depth over some portion of the dive. The computer is sampling and adding the depth changes into the model. This enables the computer to be more accurate than you can ever be. If you disagree with its model then you can do some research into what it is using as its basline profile and either buy a computer that uses a model you like or adjust its calculations according to how you think you fit its model (several of the dive computers you should be looking at allow for this latter option.)
I am not talking about diving on some recreational computer, I am talking about using a dive computer designed for mixed gases and dive profiles with a ceiling. If you are doing mixed gas diving you need a computer that can be set with the mixes you will use and be switched as you switch. Maybe you are good enough or experienced enough to get away without a computer, but I have always dived with a hand-caluclated profile (with various bailout options and numbers) in a BC pocket, a mental model of where I think I am in the dive running in my head, and a dive computer that can provide both accurate and precise info based upon its own model of the dive and diver.
You are still misunderstanding the difference between accuracy versus precision, and overestimating the level of accuracy that any dive computer is capable of providing. Depth fluctuations are just one factor in determining gas loading. Sure a computer can sample depth every second and integrate that over time, but so what? There are so many other variables and unknowns that the margin of error is huge; you're missing the forest for the trees. The profile that a dive computer will generate for you is still fundamentally suboptimal (i.e. inaccurate) in multiple ways. I am not a particularly skilled or experienced diver, yet I learned how to do this stuff with just a little practice; anyone who cares to try can do the same. I'm not "getting away" with anything.
Look, I understand that technically-minded people want to believe that there is a "right" answer and that problems can be automated away. But the reality is that no one fully understands how decompression works and the mathematical models are fundamentally not accurate enough to be useful in the midst of a dive. Better to accept a certain level of uncertainty rather than believe a falsehood. Free your mind.
The dive computers available today are simply not useful.
This is something I strongly disagree with. Dive computers are very, very useful. They can't measure bubble or various saturation levels of different tissue types, but neither can you. The models they use may be idealized and only have a fixed number of compartments for the offgassing calculations, but they provide several other benefits that make them a key component of any deep dive. For starters they track your depth over time. Everyone drifts and bounced around within a range of depths even when you think you are staying on a fixed depth over some portion of the dive. The computer is sampling and adding the depth changes into the model. This enables the computer to be more accurate than you can ever be. If you disagree with its model then you can do some research into what it is using as its basline profile and either buy a computer that uses a model you like or adjust its calculations according to how you think you fit its model (several of the dive computers you should be looking at allow for this latter option.)
I am not talking about diving on some recreational computer, I am talking about using a dive computer designed for mixed gases and dive profiles with a ceiling. If you are doing mixed gas diving you need a computer that can be set with the mixes you will use and be switched as you switch. Maybe you are good enough or experienced enough to get away without a computer, but I have always dived with a hand-caluclated profile (with various bailout options and numbers) in a BC pocket, a mental model of where I think I am in the dive running in my head, and a dive computer that can provide both accurate and precise info based upon its own model of the dive and diver.