Worl devastators are great in alliance mod: creating droid units and working as mine amplifier.
in 2.3 could construct Shadow droids, SD-9 droids or repulsor units.
the New Republic to counter World Devastators could have:
1)Carriers which unleash swarms of starfighters (like CIS station) or/also give a discount for training starfighters
2)Troopships which could train unique units (tanks, viper droids, SD-10 droids) in friendly planets for low cost; and also as a capital ship in a space battle.