Cheap T3 navy brought by 3603 had made it a bit OP, I think.
The point is while you invest in T2 ships, an UEF player can easily stop his production and give you the lead on the sea while getting a T3 naval fac and a Battlecruiser. It all costs ~9k mass which is 4 or 5 Destroyers.
But battlecruiser eats those 5 destros at breakfast, 5 more at dinner and 10 more at supper combined with shield boats.
Torp bombers also ain't help here much.
My suggestions are:
1. Rasie mass cost
and/or 2. Raise buildtime
(haven't thought of exact values)