A 2/3 carrier is not a very good design.
A carrier need to be fast. It needs to be able to close with the enemy to launch it's strike force and have enough thrust to stay out of the fight. Thrust also mean it can give it's fighters a good starting vector while a slower ship have to operate more carefully to avoid getting caught up in the fight. I personally have never liked the "battle carrier" concept, the entire point of carriers and their great advantage over battleships is the long range of their main batteries. Even without the crippling penalties that should be imposed on carriers (but are absent in BT) battle carriers are not a good idea. Yes Thera is one of the best ships around but that says more about the standard of the other designs than of Thera's excelence.