The problem could depend on your loadout. I use the onslaught in a same way because of the shockingly bad shield but I never have problems with hegemony ships being destroyed by high tech ships. it could also depend on your fleet style. I have a carrier based fleet (1 onslaught, 3 herons, 7 thunders, 5 broadswords and some gladius) I had no problem with the high tech because I could overwhelm them.