Everything being together in a deck and being quite affordable and cost effective even in phase A is an issue. That is right.
The cost is the issue not the units. It's why there is such thing as 22ap koenigstiger for 380 point in B within Lehr and there is no prob with it.
4th armored is not a phase A deck.
4th armored is good all around, that is another issue. They don't fall off like the French, which is a phase A deck who has crappy M10s for C.
Lack of 76 mms in 4th armored? What? Hordes of Hellcats would disagree. They are better than your regular 76mms, they have incredible ambush potential with their speed and aim time. And this deck can spam those Hellcats because why not? It is available and it is cheap. That is why this deck doesn't fall off. Tons of fast 76mms right from phase A to C.
4th Armored is a phase A deck reenforcing in B and that's is possible only cause of its strong phase A but there arn't really better units in C. Actually there is even downgrade with rhinos which get only a 75mm gun for 1000m and 11ap, for 30points more than hellcats. Except 4000m arty, there is no real strong C new units in 4AD it's just a fact.
And in regard of other decks they have less cards of 76mm overall.
The funny part is 2DB is quite the opposite of what you describing. They lack points to use them but they have access to way more vetted 75/76mm in B and C.
Actually there are two M10 in A, eight in B and six in C into 2DB (reminds me of something, perhaps 4AD with two hellcats in A, six in B and five in C...) But 2DB has access to a shitload of 76mm/75mm in B and C. With may much availability than 4AD actually. The trouble is they got less points in B and C and have costlier units in these phases than 4AD.
Then it's hard to say 4AD is good overall and 2DB is falling off in B and C. 4AD is mostly good cause their units are tremendously cheap for deck points flow in all the phases but in regard to other decks, 4AD lacks availability of 76mm. It shines mostly because of the cost of its units in regard of its points flow.
Simple comparaison, 2DB 75mm cost = 140 points, for 76mm = 180 points and for M10 76mm = 125 points with only 100/110/115/115 = 440 overall points flow when 4AD does have 80/130/130/130 = 470, 180 points for a few regular 76mm but only 110 points for hellcats.
It's not 4AD has access to many units or they are too strong, they are strong but it is mostly they are way too cheap in regards to their strength.
Hellcat being better than M10s and 4D having that much points flow i nthe whole game hellcats should really be above 125 points M10's, fixing price between 130-150 is no big deal.
Increase the price dramatically
Decrease the availability dramatically (especially in other phases if you want this deck to be a phase A deck, I would nerf this deck's phase A hard and maybe buff other phases because allies has many decks that are excellent in A.)
As i just said it's not about availability, 4AD has low availability, it's about price of units in regard to points flow.
Pick one of two.
And why the highest overall income? Lehr has 4700 overall income too but unlike the 4th, they can't spam their units right from phase a to c. They pay 100 points for two star mobile pak 38, aka Puma and they wait two ticks for this. Even in phase B. I am not saying that they should buff Lehr, they are good as they are.
We come back to my KT example. Lehr got very good units but very costly ones for its points flow. Why 4AD should not be the allied Lehr with the actual very good points flow of 4700 but very costly units with very low availibity...
Imo reducing points flow of 4AD in B is just looking in the wrong direction about what is going on wrong with this deck. It will change nothing.
And delete a few units in A well it's just crippling a beast. Still dangerous.