Does anyone believe a perfect fleet exists, or have they built one? From what I have seen, every configuration has a viable counter, making for fun debates but no all-powerful design. Is this correct?
Same question for weapons - it seems to me that a mix is best, but some will claim that x or y beats everything else. Is there a best weapon, or combination?
The search for one fleet to rule them all may be quixotic, but since I’m trying to find it as well you can call me Don Quixote 
The perfect fleet would need to be able to handle every situation (how this is done is a matter of interpretation), be able to function well even with loses, not scatter, and be made of ships that have no waste (meaning weapons or equipment that isn’t actively doing anything). Its all about the ship design and the orders being sufficient to handle everything.
The question is: Is this possible for 100% of what you will encounter?
I’d like to think that there is such a fleet design (or designs) so there is something to strive for.
Realistically speaking, I think the best anyone can hope for is a fleet that beats 90% of whats out there and the only way to beat it is with a fleet that is so broken that it only works against this wonder-fleet but is useless against most other fleets.
The problem here is that “perfect” is an entirely subjective term. What qualifies a fleet as perfect?
If you mean a fleet that can’t be beaten, then no, I don’t believe it exists. Such a combination would indicate a fundamental flaw in the game design (because once you found the “perfect” fleet, why would you use anything else?) There will always be something that will beat a given fleet, even if it fails with flying colors against everything else.
There’s really no perfect fleet, unless you only count the first attempt on a challenge. : )
There’s plenty of good players here, who after 1-2 attempts will successfully analyze what that fleet is composed of and come up with the appropriate counter fleet. Some fleets are a lot harder to counter than others, but if you look at the challenges with lots of attempts, you will see numbers in the victory column.
Fundamentally, the issue with a “perfect” fleet comes down to the fact that any fleet lopsidedly biased towards a certain style of combat can usually beat a fleet that is more generalist.
For instance, a cruiser laser spam fleet with good speed can carve up a generalist fleet pretty easily.
Likewise, a missile spam fleet can carve up a generalist fleet pretty easily.
It really is a fleet/counter-fleet game. Generally you can get a pretty good idea just from looking at the other guy’s fleet initially of what you are dealing with and can design a fleet accordingly to beat it fairly quickly - usually without specializing designs for that particular encounter.
A switch to campaigns, however, would add a really interesting dimension.
There are a couple of interesting rule changes that would make it really cool.
It probably gets more balanced with smaller deployments.
When you can’t gather enough fighters together to crit through an armor threshold in a few seconds, it suddenly gets a lot easier to defend against them. Likewise for things like missiles overwhelming scramblers.
Generalist fleets need their counters to be very effective for cost, because they’re suffering from the overhead of fielding counters for threats that may not exist.
Indeed, it’s probably much different to design a winning fleet when the ratio of points to pilots is between say, 400:1 to 1000:1 On the other hand, when it becomes 100:1 (battle one) or less, then a fleet has to be designed much differently. Fighters rule in those types of battles.
When each pilot is worth a decent frigate, or a cheap cruiser; that’s where it gets interesting. If you had say 50,000 points and 125 pilots, it would be a 400:1 point:pilot ratio. This way, you can field a handful of fighters, but not an overwhelming amount. You can field a swarm of frigates and know that you won’t have to deal with an insane number of fighters. Battles with this kind of point:pilot ratioing appear to be much more interesting than fighter-swarmfests.
When you open the floodgates on massed fighters, then cruiser designs change, and frigates are mostly thrown out the window.
So, the perfect fleet in a limited pilot challenge is probably much different from the perfect fleet in a fighter fest scenario.
It’s impossible to make a fleet that cannot be beaten by some other fleet.
If there was a perfect fleet, it would have been corrected during beta testing. Having every fleet defeatable is a sign of good game design.
This brings up another question. Of all of the challenges posted, which do you think is closest to being the perfect fleet?
You could get the 10 best fleets based on victory/attempt ratio with more than, say, 100 attempts, then round robin them to death and find a victor.
I think 100 attempts is too high. Many strong challenges get much lower than that. I would set the minimum around 20. Besides A/V ratio favors challenges with more attempts.