T2 subs crush all destros if in big quantitys. Little less against Aeon maybe, but it is still convincing. 1 Sera destro agains 2 Cybran t2 subs, destro wins with barely some health left. And that is kind of equal echange, as destro is slightly more expensive mass wise. But 20 destros against 41 t2 cybran subs, destros get totally wrecked.
T1 subs also crush against all destros in big quantitys, maybe less than t2 ones, but still. Note that what sandboxing I did was without particular micro or kiting.
My point is, that Sera does not even have anything to fight against t2 subs in t2 level. Making subs stronger seems like bad idea.
In the same time, the fact that navy has no units capable to fighting efficiently torp bombers, seems like a huge problem. What is the point of navy anyway, if torp bombers can efficiently kill all croisers and hunt down the rest of the ships?
I would suggest to make torp bombers weaker. Maybe two times more expensive, with same dps. And eventually up to two times stronger, if necessary. As it would reduce efficient suicide torping, while not reducing too much overall value of torps. This is just a very general suggestion.