Ummmm.....no. Expertise is vital to tanks as well, who wants a tank that gets parried or dodged alot and the dps pulls threat? That explains why the new badge defensive gear has expertise on it. Yes, a tank should have expertise, it will increase your threat, the amount just depends on what you can acheive without sacraficing vital stats(stam, def, etc.). A warrior tank in 25 man raids with no expertise will probably get aggro pulled from them often, and on a mob that is immune to taunt, what if they dodge or parry while trying to get threat back? Just my .02