The problem is that if more then 50% of the fleet is comprised of unkillable ships then you can’t win since you never meet any victory conditions even if you never lose a ship. So if your fleet has a screening element that is more then 50% and can’t be killed you can’t lose but you still might be able to win. I think this might only work on the smaller maps because if you get big enough then eventually enough ships are involved to swarm under any one vessel, but on small maps you can’t get that many vessels.
cliffski’s challenge was dirt easy 
I fail on the third mission now, but i won with 85% remaining on that challenge using some heavily armored/repaired plasma/proton beam cruisers and escorting torpedo frigates
Actually, it seems like torpedo bombers, assuming they can engage later in the fight, are pretty nasty. A full volley on closing seems have a good chance of collapsing a shield- there’s a lot of shield penetration in one small place.
Torpedo bombers certainly look really vicious, but I find they have a bit of trouble actually finishing off the cruisers. Frigates go down almost like an after-thought, but cruiser have enough armour (and possibly repair stations) that the bombers just get slowly picked off. Until you can get a bit more subtle with their attacks, I’m not entirely convinced by them.
They’re pretty role-specific. Shield breakers and frigate killers. A lot of their usefulness seems to depend on when they join the battle. Hence my experimenting with reserves. The other thing is that the first volley they fire is the most important- all the torps strike at once. After they split up they run into the problem of armour regeneration.
I’ve found that an effective counter for the torpedo bombers (and a couple of fleets that are heavily fighter- or missile-centric) is to build corvette ships. It’s the same concept that most navies use with light, fast destroyers, where you have something quick and maneuverable that’s intended to deal with other things that are quick and maneuverable. Here’s the design:
[code][config]
name = corvette
guiname = Corvette
hull = Federation Puma Frigate hull
cost = 792
[modules]
0 = frigate_pointdefence II,
1 = frigate_armour III,
2 = frigate shield II,
3 = frigate missile,
4 = frigate_engine,
5 = frigate_engine,
6 = frigate power,
7 = frigate disruptor bomb,
8 = frigate ecm shock missile,
9 = frigate crew,
10 = frigate crew,[/code]
These guys aren’t designed to deal damage. They’re designed to prevent the enemy’s shots from reaching one’s fleet. The base concept is a few Spartans (missile boats), a couple of Einsteins (beam ships), and two Iowas (heavy weapons like plasma), all set on Cooperative and Vulture. I then attach one Corvette to each other vessel with Escort orders. Incoming fighters and missiles have little chance, especially with six or seven of these guys out there, and once the enemy fleet has closed to engagement range, the Corvettes are firing off Disruptors and ECM Shock Missiles and making life difficult for those capital vessels. The escort orders keep them close, though I usually lose one or two even in overwhelming victories.
I’ve had good results with a 3-part frigate combo-
part 1= mass Ion cannon frigs- I set them on vulture, hi priority cruisers, mid priority frigs, low priority fighters
These guys fire fast! They seem to be best in mass
part 2= disruptor bomb frigates- a few of these drop shields real quick, and let the ion-frigs get down to business
part 3= defensive frigs- 4 node defensive frigs have worked out well for me- I put anti fighter missiles and point defense systems on em and float em within the mob of ion frigs- supported w/ a squad of dogfighters, these keep my frigate flotilla alive and well.
The damage these can dish out is intense- although i haven’t tested them on the challenges yet, they tend to really melt cruisers and frigates real quick. This tactic is pretty susceptible to torpedo bombers however…
That’s a lot like the reserves I’ve been using. I have one frigate type set for disrupting and breaking shields, and another just behind with armour penetrating beam weapons. Mix in my support frigates (anti-fighter/PD and some flavour stuff like ECM) and a close assault frigate design (defense and short ranged weapons) and I have a group that can zoom in on the flanks and turn a fight.