Scale is an extremely high priority to FFG. It took them much longer to design capital ships than they intended, because they didn't want to have to sacrifice scale accuracy. We also likely will never see a star destroyer, because even at the scale of the Tantive IV, it would be about 7 feet long. They have said the scales for the current fighters (1/270) and capital ships (approx. 1/500) will be the scales that the game will indefinitely continue to be produced.
I agree with the massive size of the ships.
Republic capital ships are way smaller than the Imperial versions, like the smallest type of dagger-shaped ship would be the Imperial-II class frigate which comes to 400m compared to Tantive IV's 150m.
http://starwars.wikia.com/wiki/Imperial_II-class_frigate
The picket cruisers are around 600m
http://starwars.wikia.com/wiki/Immobilizer_418_cruiser
http://starwars.wikia.com/wiki/Enforcer-class_picket_cruiser
http://starwars.wikia.com/wiki/Vindicator-class_heavy_cruiser
They are all way too big to fit in.