Well this is a thread for the GUE curious thread, so I obviously haven't taken T1.
For me Ratio, would only be used if we had an entire team computer failure, and we deviated from the dive plan so much that the dive plan is useless. So it would be pretty far down the list, but I have considered the scenario you are talking about using knots in my SMB to estimate my depth. I have one knots for every ten feet on that (and I mean the number of knots at each depth, so I can easily tell). But the time is the hardest part, as three computers have failed (two on me, and at least one of my buddy). A fourth device probably isn't going to help.
But like I said, this wouldn't stop me from taking GUE classes, in fact my physical disability and figuring out how to deal with in doubles is stopping me. Mostly because I would rather spend my one diving day a week exploring caves than playing around in the basin at Ginnie. But I am hoping to move up to CC ones of these days, so I will more easily be able to make time to work on issues.
I would put it this way - Even if you use a computer to tell you what your deco is, if you do a certain set of profiles enough times, you might actually know before you get in the water what your deco will be. If you did a dive to wreck last weekend at 150ft for 30 mins and your computer made you do 30 mins of deco and you are doing that same dive again this weekend, you would likely remember. If you do a subsequent dive to that wreck for 20 minutes, your computer will tell you how much deco for that profile. If you do the same dive for 35 minutes, you will have the data for that profile. If you note down the deco your dive computer spit out for each one of the profiles, you have the start of a table.
Alternatively, you can do some "what if" analysis using decoplanner or whatever deco software you use and write down your results in a table. In this way, you have the data for what deco you will need to do for various likely profiles before you even leave your house.
I haven't been in a GUE class in many moons so I don't know what they teach these days. But when I took tech 1, the name "ratio deco" never came up. What we did talk about is modeling different profiles and writing it down. We talked about patterns that seemed to emerge and how we could use the knowledge of those patterns.
This is not specifically aimed at you - just typing in one reply.
Finally, I want to address the notion that this somehow takes some super human skills to do technical diving that way. In my personal experience, that's hardly the case. The first dive plan I had out of tech 1 was 150ft (avg) for 20 mins. How do I know? Because instructors always tell you to take it easy right out of class. We went to 150ish ft, stayed there for a few minutes, then got progressively shallower and ended the dive around 140 ft. I don't know what the actual avg depth was but it was somewhere between 145-150ft. When the dive ended, we ascended towards the top of the pinnacle where we were probably at 100ish ft, shot a bag and then ascended to 70ft. From there, we switched to deco bottles and did 2s every 10ft until we got to 20ft, at which point, we did 5s.
There is absolutely nothing super human in this dive plan. I did it (average diver at best) and so did my dive buddy (barely any better or smarter than me). And every diver who ever took tech 1 did a very similar dive right out of class. While some of tech 1 graduates are really good / smart divers, the vast majority of us are just regular people. I suspect some people's aversion to this approach has more to do with the fact that they haven't actually experienced doing it this way and therefore haven't felt how simple it is.
