If i read correctly and carefully (and i am not sure since my brain is at the moment swimming in a very peculiar mixture of antibiotics, bacteria, virii and assorted flu-medication) then the consensus was that, yes, some things canot and shouldn't be modelled with a slow incline but with a sharp step.
Agreement as far as that goes?
That's how I view it. We might not all agree on what those technologies are, but I think that, ironically, HOI3 got it mostly right.
1) Jet engines (modeled as a separate tech in HOI3, but balanced poorly)
2) Radio coordination of ground forces (modeled as the +10% from having radios in HOI3)
3) RADAR (major tech on its own, spawns a ton of spin-off techs, but the air interception part was poorly implemented)
4) Elecktoboot quality submarines (poorly implemented on the submarine tech tree as incremental techs with large offsets; might as well have been a special tech)
5) Rockets (tons of spin-off techs with multiple applications. The V-2s are probably too efficient, but they are a leap in tech terms for HOI3)
6) Half a dozen capstone doctrines (all the special doctrines like Superior Firepower represent a substantial change in fighting doctrine and rewarded players with nice bonuses. All of the special doctrines were useful)
7) Acoustic Homing Torpedoes: One of the only weapons in HOI3 to provide a
doctrine bonus in addition to extra firepower (a positioning bonus, to be precise). Usually comes too late to make a difference, but it's a leap, that's for sure.
8) MECH: Not the best tech in the game, but for countries that can afford MECH, it's a leap forward. (I'm looking at you, US.)
9) Nukes: While the rules for researching and employing nukes could use some adjusting, it's a leap forward in HOI3 to be sure. Even if a country doesn't surrender, incinerating the capital along with its supply and resource stockpiles is a war winner. In fact, in HOI3, it might be more useful than historically.
I'm probably leaving some out, but I think that HOI3 didn't do a bad job of having "leaps" in key areas for techs. The problems usually involved how those techs were implemented. The jet engine is the most egregious example, but if it had been balanced better, it would have been a game changer.
The capstone doctrines, to me, are most striking in their there status as "leap" techs rather than evolutionary techs. It's hard to get them all, but they are all useful to just about every major power (the only exception I can think of is the width reducing tech for MIL/GAR for the US). They have a huge impact on the game, but they aren't incremental. I actually really like how they are implemented in HOI3, and I'm curious to see how they are set up in HOI4.
I know they aren't "equipment" in the same sense as nukes and jet engines, but they may have the effect you are looking for with certain kinds of equipment.