Pretty much what Keonobi said... Heavy artillery cannot destroy them? Come on? Seriously?
Like I noted, Jedi can cut them easily with their sabers... But suddenly the big guns the Republic has do zero damage? I can see one being a menace and tough to take down (like Keo said, multiple AT-TE's having to engage it), but being completely impervious is, at best, a plothole. At worst it's writers just pulling something out their ass to make something more exciting.
The series has an element of realism to it often times, and with this it was lost completely. "Super-weapon-of-the-week" syndrome. I hope the series doesn't fall into that pattern.
I also agree with the tank's design being flawed... The mortar guns are cool for sure, but having it look more tank-like with a main gun atop it would've been nice. As it stands it's got anti-personnel guns at the front ala the troop transports, and mortars. It's kind of a weird hap-hazard design. I really disliked it a lot and think it's best left shelved at this point, which I hope is the case since they were describing it as their secret weapon, and the first ones rolling off the line I guess. The Tiger-II, it is not though.
As far as Anakin's traits, I believe that possessiveness and the inability to let go are one in the same. I don't see those as being different at all. He'd waste 1000's of Clones to save Ahsoka, R2, and so on. He's loyal to a fault, as far as the Jedi are concerned, but also it's greed ultimately. They're just different ways of saying the same thing I think.