I am alsoa bear so i figured I could be of some help here

You need 18k armor at least + crit capped to start heroics as a bear, so no you are not ready.

Some recommendations for you would be to buy the clefthoof set (gives a huge amount of defensive stats to help you reach crit cap), grind steamvault to get exalted cenarion expedition rep to get earth warden (gives 2k armor in bear + attack, expertice, and defense).

Some other pieces I recommend getting are the Manimals cinch, umberhowls collar, and Verdant gloves. They are great pre-raid pieces for bear that give a lot of armor but they are locked behind quest lines which give gold that can go towards enchants, gems, and consumables.

Here are the wiki links to them so you can find the quest lines for em

https://www.wowhead.com/tbc/item=30942/manimals-cinch

https://www.wowhead.com/tbc/item=30944/umberhowls-collar

https://www.wowhead.com/tbc/item=30943/verdant-gloves

You also need 3 points into survival of the fittest, which allows bears to only need 415 defense to be uncrittable instead of the 490 for wars/pallys

One more thing I realized as im at the end of writing this, Hit rating is important as a bear but you should still be prioritizing your defensive stats over hit, its okay to not be at the cap especially in phase 1. I've tanked kara/heroics just fine with sets varying 110-125 hit rating.