they cost 30 manpower, not terribly expensive, but really not cheap either!
300mp unit reinforcing for as much as 240mp unit.
I don't even need to argue here, numbers do the job.
they dont scale well and get outdamaged pretty fast by elite units or weapon upgrades. furthermore they dont vet fast, cause they dont have any AT (imo infantry gets too much exp from vehicles, but that is another topic)
They beat tommies, they beat conscripts, they beat rifles, unless they are upgraded and weren't approaching over red cover. They are utility unit, not a shock troop, obviously they get outperformed by elites, they are NOT elite themselves.
They vet reasonably fast, not faster or slower then any other infantry unit and by extension of your logic, apparently no unit can vet decently if they have no AI.
as they are a 4 man squad and have normal armor and have to close in, they die pretty fast. if you focus them...
Again, they are NOT shock troop, the armor is irrelevant, only single infantry unit in the whole game uses armor, they have decent rec acc bonus from get to making them more durable.
4 men is NOT an argument, allied weapons are DESIGNED to go against 4 men squads, so it makes no difference unless you run frontally vs HE shermans or over mine fields.
And last but not least:
ALL units die pretty fast if you focus them, even shocks go down quickly to volks if they focus them.
The unit is fine, isn't overperforming and doesn't lack anywhere.
Its a T0 STARTING engineer unit, not ubermenshen(this line goes both, to you and to OP)