High speed (thrusters), short range weapon armed ships are useful for anti-piracy where you want to close and kill before the attackers can damage your mining stations. But for large scale combats against opposing "main fleets" and attacking planetary defenses - range trumps speed. Long range allows you to focus the firepower of the majority of your ships on specific threats - troop transports trying to land troops, or some big, badass ship that the opponent has. High speed ships need time to turn and close, which is time you won't often have. Not to mention when the Shak show up, whose speeds severely outmatch yours and you won't be able to close with them, much less destroy them before they warp out of the fight. For them, you really need lots of long range firepower - if you have more firepower but it's all short-range, they'll just keep moving away and you'll never be able to catch them to do serious damage.
For attacking planets, it's much better if you can retreat your damaged/shield-depleted ships before they go pop. If your ships are kitted out with short-range weapons, once your ships start trying to get away, it's probably too late and they'll go pop.
That is, of course, if you micromanage the battle. If you let the computer do everything, it's random choice of targets means your short-range ships will be spending a lot of time running around and fighting at poor range effectiveness; while long-range weapon armed ships will be far less troubled by the random target allocation.
I don't design much, and spend my abusive power in micro management of combat (when needed). There are only so much effort you can spend before the game is lost to boredom, so I leave designs alone...
The fast moving pirate hunter is mostly relevant in early game, when pirates are a threat. Once some tech and development is in place, pirates are pushed far away, and are easily killed. In addition long range scanners help a lot in catching them. Also, shields on mines become better with tech. They may also be lucky enough to be built on the "AI side" of the galaxy, and not killed by me. I think that is major reason for their absence after a while, they are all far away prospering on poor AI.
I prefer my ships powerful and with good shields. Once I have new (AI) designs out, and notice them stopping at an distance to pop the defensive base (or similar), it is straight into the design file to specify "stronger opponent - all weapons". This is not in a prime spot to get away, but usually I don't lose much brawlers after the "early phase". Cruisers with some tech usually manage to limp out.
I think my last AAR was typical for me. Battle fleets of 10-12 cruisers and 5 or so carriers. In that game the cruisers were short range with good damage (like I prefer them), and what was usually lost was carriers. And my carriers are not on "all weapons"... The carrier should stand off or evade, but once enemy ships target them they are stupid and too lightly shielded/armored to get away. The AI manages to try keep range to one opponent, once there are two, it seems to just notice one of them, and could if necessary try to escape its aggressor by going through the enemy spaceport.
For the micro managed planetary defense, I don't think speed/range is too important. When a fleet is incoming I tell my fleet to move to the colony. They will end up somewhat circling it, either in arrival, or in "drifting away". On enemy landing, I tell groups of ships to target nearby troop transports. If the AI is control, I doubt it matters much, as targeting is probably quite random. Whatever method used, stopping all transports is hard, as they tend to not die instantly when targeted.
When I notice a ship taking serious damage some way into the game, I figure it is mostly fighters to blame. A somewhat upgraded fighter cloud carries a serious punch, and they seem to focus fire at the start of combat. And if I order my fleet to "kill defensive base", then "kill spaceport", enemy ships present adds some pain too once shields are depleted.
When doing assaults on dangerous targets, I try to fight one at a time. Even if sometimes arriving a tad too close.
That fleet was extra strong, built to bust powerful defenses, which include legendaries. The AAR reported "1 cruiser missing" afterwards. It was possibly disabled and not killed.
I think you can be very fancy in ship designs, but brute force in deploying them works too.