Have you used Metanium? It really has been a miracle cream for all three of mine. Like thick yellow wet chalk and you use just a tiny bit so that it is just the thinnest layer (dot in on an pat gently to spread). I swear I noticed a difference by the next nappy change.
It healed the broken bits on dd very quickly and now I keep a tube all the time and use at the hint of nappy rash starting. My dts nappy rash has never got quite as bad as dd's did I think due to getting it on early.
Please try if you haven't already, its great.