Agreed Tank stance for the chicken is completely useless beyond the HP buff it grants the bird.
I only bother putting mine in Healer or Free stance. I have only ever had to use Healer stance in a few situations where I did not want the bird actually killing the target, usually because I had to /sooth it or something.
In Free stance, he heals me often enough, 99% of the time.
FYI, my bird has been lv20 for almost 2 years but back when the max was lv10, I spent 10 points on Healing (Skills 1-4) and the rest on DPS.

As for a revamp, how about some dodging logic. You know, if there is big circular AoE on the ground and I run out of it, my bird should follow me.