Well we have a problem then...
I just battled the exact same line up and this time kenobi wasnt taunting but had debuffs as before. Bariss attacked r2, r2 countered and hit bariss. The debuffs cleaned off kenobi as before but this time r2's stun landed and stayed on bariss.
In the first example r2 stun cleared when bariss cleared debuffs after the debuff was applied by a counter against a taunting ally.
In the second she cleared all debuffs before the counter debuff landed on her.
There is something not right here.