The problem here is, people always assume the league races are worse.
Lets not forget the Abbai have shielding technology and are nearly as old, and possibly advanced as the Minbari, the Brakiri have more money than pretty much everyone else, those two things combined should have no problem whipping up a bigger ship.
The League are the league as they themselves don't have the political clout of the other races, this doesn't mean they are backwards and unable to produce something state of the art, look at Britain, tiny Island, yet we can still produce Items of better quality (well, the military can) than a Chinese operation, yet they have vastly more people, bigger armed forces, communist state to get things done cheaper etc.
the EA had just gone through civil war, half their fleet was wiped out, their planet quarantined, it's perfectly likely that in that time frame, they couldn't build a dedicated armageddon ship, whilst other races can. (same argument may go to the Narn who had been under centauri control)
People often look at EA, as the portrayed race in the show and automatically assume they are bigger and better than everyone in the show, apart from where blatant, in the minbari and ancients, you have to remember, sure, they beat the dilgar when the league couldn't, but then apart from the Drazi, Humans are the most warlike nation in the galaxy anyway, doesn't necesarily mean they had better ships, they just used em better, at no stage is their anything that specifically states that the EA ARE technologically better than the league races (someone will drag up a line now won't they)
plus, lets face it, with the exception of the victory, and maybe adira, most races would be better taking 2 warships anyway