Here's my understanding of the Dura Ace 8 spd STI situation:
DA8 cog spacing is the same as any other shimano 8 spd cog spacing. If you have a freehub body that can take 8/9/10 spd shimano cassettes, any 8 spd cassette will work. To move a DA8 derailleur the correct amount, however, you must have DA8 shifters. Cable pull is different in the shifting mechanisms of other 8 spd STIs. Concordantly, the DA8 derailleur has a different cable pull ratio than other shimano derailleurs.
So yes, you need DA8 STI's, barends, or DT shifters if you have a DA8 derailleur and want to run 8 spd.