I also think the tank is pretty strong!
After all, this thing always counts as defended (so 5+ to hit) and has a save of 3+.
And it is just one base, so you can all but forget to attack it with infantry from the front (you get just one base to attack), and with cav. you need a strong unit and it's still an even match - remember: no bonus attacks for attacking in the open (it does not explicitly say so in the rules, but as this thing counts as defended, I would play it that way).
I think this thing is pretty evil.... playing Dwarfs, I'd definitely love to have one of those!
M