Right now, Escourts are overpowered because they kill things really fast with their high DPS, can turn really fast, and there is no death penalty so they can just keep rushing in and dying as long as they kill something before they die.
Cruisers are a bit gimped because they turn super slow, and their warp cores can't support firing all weapon slots full of beam arrays. Their extra hull doesn't help them live for too much longer, and since there is no penalty for death, it's not really worth it except for the beauty of the ships.
Science Vessels are better tanks than Cruisers because they have more shields and they regenerate faster. Science Vessels also turn faster, so they are in every way superior to Cruisers except they have 1 less weapon slot, but that doesn't matter because their average DPS is probably the same or better due to their better turn rate.