This looks pretty sweet. Maybe if you increased the focus to be on other defensive abilities (maybe some spell resistance?), making up some, and giving as bonus feats other defense-inhancing ones (like maybe improved shield bash?) then cut BAB to 3/4 or (dare I say it?) 1/2, so its more of a "you cannot ever EVER! kill me! than a trade blows for the squishies. At least, thats what the name "Tanker" makes me think of.