Honestly, D-Shield is in a fantastic spot currently

Given what it's supposed to do, it actually does it very well. It's very good against heavy auto attack based champions. The sustain was cut down on it some time ago because 10hp/5 is absurd in combination with anything running +hp regen in masteries.

Doran's Shield CANNOT be a great item that's desirable the way d-blade and d-ring are, when it's that good, it makes certain champions too powerful (anything with sustain for an example) and it generally makes lane phase very stake in solo lanes. It's doing exactly what it's supposed to do now: counter auto attack based champions. I could see removing the regen from it and reducing its cost to 400, allowing you to purchase two pots, but as it is, D-Shield is very good at what it's supposed to do. It's not for EVERY champion, but the champions who use it are very efficient with it. Buffing it is only going to make those champions early games stronger (if they're strong early) or harder to punish (if they're weak early).

Take it from a Nasus main, you don't want D-Shield buffed.