Tremor is basically a weaker Earthquake. At that point, you're just making a gimpier caster.
Apart from Dire Bear form, druid 9 gets you lvl 5 spells; Animal Growth is the most useful one to this build.
Even without knowing his exact build, I'm reasonably certain that ES and Stalwart D. are doing the heavy lifting in terms of tanking, particularly his HPs. Bear adds some modest PRR and couple of buffs (Rising Fury, Roar) and not much else.
EDIT: wolf form gets one big bonus (+30% atk speed) which can offset its many disadvantages (poor crit profile, lack of +[W] bonuses, etc.) if you build around it. Bear-form bonuses are a lot more modest and don't come close to making up for its poor melee DPS, IMO. My druid 9 / ftr 8 / barb 3 is my best guess at the most viable melee bear option, but that's not the same as saying "good." YMMV.