Well, there aren't any tier 10 TDs (yet). Problem with the JT is, that as soon as someone knows your frontal weakspot, you are fucked. Hull-down is the only thing you can do then and this is not always possible. Also with the latest addition and tweaks, a lot tanks can now penetrate the JT tower, making the armor pretty useless. Especially because so many people are using damn gold ammo nowadays, which penetrates anyway and makes you gun meat...