My group used a crit table for a while, we even had different ones for different kinds of damage. It was fun at first and certainly can add dramatic narrative as you intend, but eventually it just began to feel kind of intrusive and overly complicated and we decided to go back to the RAW. We still narrate crits, but the mechanical result is always just a bit more damage.

At any rate, I think it's worth trying out at your table. I'd suggest setting a number of sessions to test it out and then gather feedback from your players and decide where to go from there.