I disagree with basically everything you wrote.
Panzerwerfer isn't worse than other rocket arty. It's actually one of the best rocket artillery units in the game. Not sure why you would think it's worse than LM or Katyusha. Calliope is better but also more expensive. Stuka is debatable because they function in different ways.
The 2x cheaper unit > 1 expensive unit argument is pathetic and doesn't say anything about how good the units are. Brummbär could do with a slight buff but 2 Ostwinds being better than one Brummbär has nothing to do with it. It's just like saying two P4s do more damage against infantry than a Tiger, therefore, the Tiger is bad. It makes no sense.
Panther is an excellent tank and in the best spot it has been in since I started playing this game in 2016.
So yeah. How this makes Ost T4 bad and useless (your words) is beyond me.
Which is fine, you're free to disagree.
I grant you the Werfer is better than the LM, but that's because that one takes the spot for most worthless rocket arty in the game. The problem with the Werfer comes down to a single thing: Consistency. If I use a Katyu or a caliope I can be certain they're going to kill something. With the Werfer, it's often times either nothing, and then your next volley wipes two squads instantly. It's an RNG cannon much more than the two mentioned above, even if they don't have the same raw wiping potential (which often times isn't fulfilled) that the Werfer has. Agreed on the Stuka zu Fuß, since it doesn't work like the others.
Both Brumbär and Ostwind are dedicated AI units that fall into the same niche. Only the premium version is actually inferior here because it can't fight light vehicles like the Ostwind can and it doesn't shoot down planes either. So the point that two Ostwinds are better is not just relevant, but incredibly important. I can get more and better stuff for the same price. Why then would I ever choose the Brum?
Your Tiger comparison falls flat because the Tiger performs a completely different role. It's your elite unit that will reliably handle anything on the field that's not a heavy tank. By comparison, the Panzer 4 is the ultimate jack of all trades medium that doesn't particularly excel at anything. And personally, I would put my bet that a single Tiger deals better with infantry than two Panzer 4s. Which is exactly what this entire discussion comes down to.
Again, the Panther is a decent tank. In 4v4, they're definitely the better choice than the Stug. But that's not what I was saying. If I invest as many resources and risk as I have to in order to get a Panther, I expect it to solidly out-do my T3 AT units. But it
doesn't, which is the problem.