It's a strong doctrine, but not op anymore, the tiger ace comes very late, so you have enough time preparing for it and the enemy must spend his fuel to vet his units. It's with no doubt strong, but not op anymore, if you can manage to kill the tiger ace it's pretty much over. The only thing i don't like on the tiger ace is the stunshot which makes it a little bit too good for my taste.
1. Not true. It doesn't arrive 'very' late in the game.
2. That's the thing, it's just really strong (not OP) but still a pain in the ass to kill because so many AT-guns just don't penetrate the damn thing.