OPs points are valid and back up my own experience.
Several points...
Unless the bug has been fixed ( which no-one is saying) your tests were very strange at best.
Even your tests only showed parity in the IS's strongest suit.
Your tests conclusively showed that IS get destroyed out of cover.
Your tests were not real game centric. Add in a grenade of some description or of mere moving and firing and the Tommies get chased out of cover and are destroyed quickly.
IS of such configuration are both expensive and unuseable in game. Feel free to build them however losing 60 or 120 MU per engagement is not a good use of resources.
The tests were not strange, in that they were simply showing top vet OKW infantry against UK top vet infantry. He purported to be doing no more than that. Indeed, it was making a contribution to the thread, which says that OKW elite vet inf is too strong against UK inf. That implies combat effectiveness when fighting each other. Indeed the OP said:
Spend 300mp, 50 fuel and 120 muni for double bren tommies? too bad one vet 5 Jaeger squad seems to solo your units anyway while he buys tanks.
He is saying that one JLI can solo your units, which is quite obviously not true. The video is a rather helpful in rebuking the OP's general point, which seems to go to nothing more but isolated 1v1 (or indeed 1v2) combat effectiveness. In any case, this is arguable what they are designed to do, counter infantry. What else does OKW have in their roster that counters allied infantry? The HMG that is shit and doctrinal? The Panther? Save up for a KT? Flack half track (lol)? The fact of the matter is that that, if their elite infantry does not beat Allied infantry, what else will?
If we are to take your point about grenades (which Tommies also have) and "realistic game scenarios" on board, then a huge number of variables would need to be taken into account. Some of these include:
-First and foremost, is that it is extremely rare that Obersoldaten get to vet 5, same with Pzfusils and JLI. It is extremely difficult with most OKW elite infantry, except for fusils, because they have 4 models, and often terrible unit spacing.This means that, for the most part, your units will get wiped extremely easily, by tanks, arty, mines, etc.
-As a follow on from the first point, you are always at a vet disadvantage with elite units, because Tommies are out much earlier, which gives them the chance to earn vet before you do.
-Then there is the fact that with 2 out of these 3 OKW units you will have no HMGs to provide support, whereas UKF to. This obviously decreases OKW's combat effectiveness.
-Then the fact that many UKF tanks are more versatile at dealing with infantry aswell as vehicles, and you also have good AI late tanks to depend on, unlike OKW.
-OKW on the other hand have the advantage of more indirect fire
The core question is really whether OKW infantry is over performing. With the exception of Pschreck Volks, I don't think this is true. They are just designed strangely. In some ways they are, in others they are not. They become incredibly powerful because they are difficult to counter when backed up with 4 Volks, because vehicles are so hard to use against them. On the other hand, in many cases they arrive late, take ages to vet up, and also are prone to getting wiped.
I think they just suffer from bad design, rather than being over powered. They have a huge power spike, which is difficult to counter. But saying they are overperforming without large caveats is not true, by any stretch of the imagination.