The key to balancing 2v2/3v3/4v4 is to bring the principles of 1v1 into the bigger games. If you make OKW play by the same rules in 4v4 as 1v1, they become a lot more manageable, without screwing up balance in other modes.
In other words, no need to nerf to the Jagd, just make the faction play like it does in 1v1. If a guy manages to get out a Jagd, then their team probably deserves it.
The only possibility of bringing 1v1 principles into team games is if Relic starts to scale the resource incomes and costs of units depending on how many players are in the game. Otherwise it's not possible. Since I don't see them ever doing that, I think a nerf on the Jagdtiger in some manner is the only way to balance armor in 2v2 and up.