Now, i have some broad questions about specific researches(civilian category) and their usefulness(diplomacy 1.00 here). I'm interested only in sp, not that ultra-specific 5vs5 multiplayer where 50% of the gameplay is just automatically obliterated.
Uh, you need to update your game. A lot of things, especially pirates, were totally different in Diplomacy 1.0.
Honestly, for the most part it doesn't matter what techs are good or not in single player. Sure, you want to get the good ones first, but you can research everything without too much difficulty against the AI. Human players can rush you, which means by default you research the minimum amount to win. It is very hard to get a good idea of the game's balance with just a single player perspective.
Civilian ship safety act. In what way it's remotely useful other than when an enemy occupies a gravity well between my colonies? Even then, is it really important to spend 800 credits, 100 metal and 175 crystal for even the first upgrade? Second upgrade seems utterly pointless, at least imvvho
Like any game, some things are pointless, others way better than average. If trade ships took a while to respawn it might be important, but they don't.
Catastrophe recovery. 1200 credits, 200 metal and 325 crystal for first upgrade? Only 13% build rate of recovering infrastructure after bombardment! Does anyone even research that?
Probably not, unless you don't have any more ships to build.
Advent. 1) Communal labor. In what specific way is it useful? I see only very specific reasons - very heavy destruction of planetary defenses and big need to rebuild things FAST.
Increasing build rates is always useful. The sooner you build a factory or trade port, the sooner you can use it to make ships or money. Also, against the AI, you can often get away with building defenses at a planet while its under attack, so obviously speed matters a lot there too (the AI got better at killing your constructor ships in the Rebellion expansion, but its still sometimes possible).
2) Lingering presence. First the research cost(2 upgrades too), then the scout cost. So if i use like 10 scouts for that(and use only first upgrade), i kinda use 260 credits, 5 metal and 10 crystal per scout to get information of some gravity well for some time. Isn't it easier to just to shift+click the path 10-.... times or something back-forth?
I actually like this one. First of all, if you use the auto scout feature, your scouts like to hit the pirate base a lot, which is usually suicide. Lingering presence means it will be revealed for 5-10 minutes or so after it dies, so your surviving scouts won't be as suicidal since they don't go to revealed planets.
Second, odds are if your scouts died in a given gravity well, that's a planet you want to keep your eye on for a little while.
Third, yes, by all means use the jump back and forward method. However, those 10 scouts will all still die at some point. Even if you're just using it to keep an eye on your neighbors front line, you can wait a few minutes after the scout is killed to build the replacement scout.
Resource focus + enhanced focus. Okay, the first one is utterly pointless, but with the final upgrade the % can be beneficial. Only problem is... research cost - About 4200 credits, 750 metal and 1225 crystal. By the time those researches are done, the game is almost over(lvl 7). Anyone can point otherwise?
Compared to trade, refineries and resource focus are pathetic. In my Enhanced 4X mod I had to increase the output of both by something like 25-50% to make them competitive.
Karmic retribution. So no pirates, no point?
Actually no. Bounty is mainly for pirates, but any player besides the one that issued it can collect it. So if you happen to notice an enemy player is destroying a lot of your trade ships, you can research this to encourage other players to attack that player. Or in team games, I believe your allies can collect it, so it can become an indirect way of giving them free money.
Still, don't research it until you notice its happening a lot.
Wreckage auto-salvage. The first upgrade costs 800 credits, 100 metal and 175 crystal and it gives 5% per some destruction only when the capital ship is in the same gravity well. The next upgrades are even more costly. When doing the lvl3-4 researches, there are way better places to put money into. By the time it can be beneficial, i'm already at something lvl 6-7 in research and it kinda seems pointless to invest in that research cause the game is already at the ends. Yes, in very long games it maybe is useful.
Well, if you kill another capitalship with your capitalship, you'd get 150 credits right there. In the longer term this one can pay for itself. If you don't want to fleet up for whatever reason, it is a very safe bet for extra resources.
Phasic barrier. Only when extractors are under attack. Any other points?
Actually, this one makes the AI go crazy because it forces its ship to retarget a different structure... which might also have phasic barrier. Even other players have to deal with this annoyance by constantly ordering their ships to attack a trade port. So its not terribly important, but it does slow down the enemy somewhat, which can be useful.
Shock and awe, which gives culture suppression 20%(when capital ship is in the gravity well) with first upgrade and further 20% on second upgrade. Lvl 5 research. In what way it's useful to just sit with your capital ship in the gravity well while it could be better to attack with the capital ship directly or just move into other frontiers(just make another media hub and sacrifise 4 module slots and off you go, less resources spent). The only useful point i see is when there are 2 capital ships going forth(attacking) and back(repairing). Okay, maybe 1 is enough. But that's only temporary setback in allegiance(and some income).
I won't say that the research is good, but sometimes you have no choice but to leave a capitalship at one of your planets to prevent a culture takeover while you build some more culture centers for the long term problem. So if you find yourself in that situation a lot, this would have some benefit.
Oh and did the patches make changes in those researches?
Probably not many of those, though I do think communal labor got changed at some point (my comments reflect only the latest version, no idea what Diplomacy 1.0 had). The Rebellion expansion of course added entirely new research as well.