Well I've now achieved it, both uncrittable at 490 Defense and uncrushable at 102.4% (Miss/Dodge/Parry/Block) total avoidance value while Holy Shield is active for a Paladin. All Pre-Kara & Pre-Heroics. All unbuffed at 10.4 HP and at 4188 mana. All my gear are either Quest Rewards, Revered/Exaled Faction Reputation gear and 3 pieces of Crafted gear one piece a Epic Crafted piece. I have no Heroics or Karazhan gear as I have yet to do either.
All I did was log in and played around with a some pieces of gear I collected recently. In my normal gear usually worn I have a max of 11.2 HP but in that set I'm uncrittable but much crushable Pre-Kara. With Libram of Repentance from Heroics that would also give me a lot of different gear options for both uncrittable and uncrushable gear set combination.
Combined Avoidance without Holy Shield active and with Holy Shield active using the Avoidance Macro to easily calculate combined avoidance value. Just a little bit over 102.4% for uncrushable through various combination of a few select pieces of alternative gear. Another reason to KEEP ALL YOUR GOOD GEAR!
I have about 4 different combination of gear sets using ItemRack addon. This just the gear set listing that I'm wearing for uncrushable set. My Armory set is a different set I usually wear and interchange trinkets & weapons when in instance. Will have do a posting where you can obtain all that gear in another blog posting.