Usually I do run as high locking I can steer on coast, this is to make excessive engine breaking safe (or I will push the inner wheel backwards giving a spin). If I run high locking on power, the tyres dont last too long for me, but (read my sig) power steer is fun. The RAC with a locked diff does not steer at all, you slide it until it points at the exit and power out.
Locked diffs are quite common in RL, and the tyres take the damage, not the axels (since the setups makes the cars behave like gokarts but with alot more front/rear weight transfer)
I only race myself, and I only race for fun, so I don't bother about physics exploits by me or other drivers.