There is a superior set of expansions made by the excellent Rbax. Check 'em out, scenarios and everything. Earthforce's entry into the War is still pending, but the Brakiri fleet, in particular, plays very differently in olden days...
If you want to count all the reasons for the Dilgar's defeat, don't only look at technology but also at numbers. :? They were outnumbered and at the last of their strenght...................Poor Dilgar, Mhuahahaha......... I play against them as if they have never been destroyed, and they are a tough nut to crack 8)
The Dilgar are interesting to fight. The problem I have seen is that players tend to gang up on the Dilgar because of how the race was in the series. This forced the player in our campaign to play the Dilgar as pariahs, allying with the Shadows because the Minbari player was waging a Jihad against them from the start.
Against period vessels they are indeed a tough opponent.
Strange observation. I haven't had a great deal of opposition, perhaps because my local opponents aren't fighting Dilgar, just fighting me running Dilgar. It could also be because I've been horrifically destructive with them; and, in a campaign, it's a whole lot easier blowing up ships than building 'em, so players try to get someone else to attack the Dilgar.
You say "against period vessels". We think the Dilgar may be vile against any vessel. The base Targrath, locally, is locally considered to be busted. Does your group disagree? Have we erred?