No, it is effective through various ROA's (IV, IM, subcutaneous, intranasal, rectal, oral, sublingual, etc ) just like any other opioid. It is prescribed in various pill forms (instant release, time release/extended release) which is meant to be taken orally.
I agree, and would say that an 8mg dilaudid feels like almost 40mg of oxycodone taken orally (which as you mentioned would be like 30mg snorted since you get less oxy when sniffing it). It doesn't last as long, but I snorted each 8mg dilaudid over about 25 minutes which increased duration. Snorting it over a longer period of time also allows for better absorption compared to sniffing it all at once since doing it all at once would cause some of the binders/fillers to prevent a little bit of the hydromorphone from coming in contact with the mucous membrane as opposed to doing small lines over time which allows time for the membranes to be cleared out and ready for more of the drug to come in contact with it.