Yes, there seems to be an online calculator to sort out where your toon stands re being uncrittable post-patch: A list of useful Tanking Formulas for Warriors - Dodge, Parry, Block
You plug in your resilience, and it tells you the defense rating you require to be uncrittable.
Also, not having regemmed/re-enchanted since the latest patch (when our defense rating plummeted ~ 20 points), I find my prot warrior toon is "overcapped" for defense, and I can free up 12 defense rating points - that with current defense rating of 482 and resilience of 33 - and remain uncrittable. See Be Imba! - the online Character Auditor for World of Warcraft
The moral of course is uncrittable is a combination of (at least) two components: defense rating and resilience.