Please explain more. I don't see what it is with this that you see as unbalanced.

For example.

If I have a vessel with 5 in beam, 5 in shields and 30 health against 10 ships with 4 in beam, 4 in shields and 20 health, my ship will win.

If I have a vessel with 2 in beam, 10 in shields and 30 health against 10 ships with 8 in beam, 1 in shields, and 20 health, my ship still wins.

My ship costs  much less than the sum of the enemy fleet, the stats of ships individually speaking are quite similar, however they out number me by a significant amount. I would expect to lose this fight while taking a few of them with me, but with the system of the perfect Defenses GalCiv II has, my ship takes zero damage while eventually destroying all of theirs.

It is a balance issue because it encourages only one style of fleet construction. To maximize the quality of your ships, and ignore numbers.

TLDR I just want the idea that a swarm of ships would end up being viable against a single high quality ship. Otherwise, the larger hull size will gain an unbeatable advantage over the smaller hulls with the same tech. It encourages rushing of hull sizes too much.

it really is just simple math. Given the same tech in miniaturization, weaponry and defense, a larger hull, even if its just by a small amount, would have say X amount of extra space.

Assuming the smaller hull's stats are Y and Z, for offense and defense, just make a ship match your larger ships Defense for Y + X/2 and offense for Z+X/2. And voila, your ship just gained an almost unbeatable advantage by simply going up one tech in the tech tree (hulls).

Even if I am 10 techs ahead in production and is far ahead in economy, regardless of how many ships I send, your ships will be at too great an advantage for me to overcome. Especially given the idea that fleet size is limited initially so I cannot actually cram 10+ ships into one fleet in the early game, and that multiple fleets at the same location cannot provide any assistance, your comparably small fleet of slightly higher quality ships will just bulldoze my entire armada until I can match you in hull tech.

I think he is exaggerating but I have noticed it as well.  I have no idea where he gets perfect defense from but I do know that if your ship has enough defense to mostly neutralize one enemy ships attack, it will mostly neutralize 100 ships attack.  Or a 1000.  If your defense is say 15 and the enemy has an attack of say 5 the enemy needs so many ships to bring you down it isn't practicable. Basically, he is waiting for the dice on your defense to roll low and the dice on this attack to roll high and he has done 1 or 2 points of damage.

This isn't a matter of perfect defense, it is a matter of the fact that each ship has to bring down the enemy ships defenses on its own.  There is no way for your ships to coordinate their attack to try to overwhelm their defenses cooperatively.

I do *believe* that the defense ability for off type defenses are rolled first before the square root penalty is applied.  This would make off type defenses favor the high values of their limit.  If you have 25 defense a roll of 16 or higher will give 4 or 5 against off type attacks.  This may offset the penalty enough to neutralize entire fleets of ships with 3 attack.

This was a change, in earlier versions of GC2 a ships defense was rolled once and it had to last the whole round.  So 5 smaller ships would wear the shields (or armor or PD) and ship #6 would get to do damage.

I am not sure what the rational was for this change but it had the effect of buffing defense as well as narrowing the technology gap that empires could have and still wage effective war.

As for the original question of will this be fixed, we already have a good answer that probably yes.  We know that the whole tactical situation is getting an overhaul.  It is very likely that this system, like it or hate it, is going to be irrelevant in the new game.

Twilight of the Arnor introduced "Defense Degradation", with your maximum potential blocking of damage being reduced with each blocked point of damage. I frequently lose singular Battleship patrols to large swarms of AI on the higher difficulty; my battleship, a near-impervious dreadnought of death and destruction with 150 attack and 300 defense will lose to a 15-strong fleet of frigates after killing maybe ten at most. 

Against a Human player, that would be pretty bad, but against the Suicidal-level AI (who pump out battleships by the tens of thousands) it's nothing. The only real way I have of mitigating this is to use frigates of my own and match them roughly 1:1 in fights.

Especially with higher logistics numbers, tiny hulls could take down a bigger ship pretty easy. The main reason no one did that was that the tiny hulls couldn't have engines if they were going to have any significant amount of weapons.