"Nah, they know it's the early game, nobody builds mines then." Heh, I should have acted on my perfectionist impulse.
Aside from a few Advent mine-lovers, it's mostly just Vasari that use these. TEC actually need to build them with construction frigates, which just takes forever and a day to lay the minefields, and the Advent need to expend antimatter on their precious carriers to do it, plus fighters can intercept the minelayer squads. Vasari? Pop! Mines successfully deployed.
Could you elaborate on this statement? I know why Ice/Volcanic tech is important (no kidding), and I know why repair bays are important, but it always struck me that things like reducing building costs by 30%, increasing build rate, increasing trade vessel payload, and broadcasting culture, are all important. Hell, even the tiny metal/crystal bonuses could be considered important, if only to counteract the upkeep costs of a larger fleet.
Those things are all well and good, but their impact is more passive and long-term. The low-lying fruit (1-2 lab techs) are inexpensive and worth your time if you can afford them; the major cost there is the labs, and if you already bought the labs for ice/volcanic colonization, the other goodies are useful. The problem is from level 3 and upward the cost of researching these things starts to take off, and the labs are no longer a sunk cost. In these cases, you're often better off putting all that money into your fleet so you can hurt the enemy
now rather than getting these technologies that will pay off in 10 or 20 minutes.
Now, culture is another matter, since it can
threaten the enemy in a literal sense. However, it's still not critical in most cases. If your opponent just has one or two culture centers, you can actually negate their effect just with the presence of your capital ships. If you're pumping your cash into military and are actively pushing the enemy back, the culture centers won't have nearly enough impact on you and might not even slow you down. If you get stuck in a stagnant position or a long-term fight, then culture becomes necessary.
Also, if I could be so bold, do you happen to know which military technologies for each faction get the most bang for their buck? For TEC it's armor and ship health; combined with the Hoshikos, your ships just won't die. But what about the Vasari and the Advent?
Health and armor upgrades are always your best bet, simply because they affect
every unit type, whereas weapon upgrades only affect some units in your fleet. Advent also gets cheap shield upgrades, so those are useful, but for the other factions they're more expensive and less effective than health and armor. Depending on your strategy, antimatter upgrades can be worthwhile.
Aside from that, there is only one faction-specific must-have tech: phase missiles. This weapon is simply astonishingly powerful for Vasari. Late-game, Vasari phase missiles are easily the most fearsome conventional weapon anyone can employ. This upgrade is also used by surprisingly many high-utility units, including the long range frigate, flak frigate, fighter, bomber, and starbase.
Lastly, do you have any suggestions regarding defenses? I tend to dislike spending money in defensive units at anything other than a choke point, since that limits the money I could be spending on either my fleet or my economy or my research (or all three).
That's the right way to feel; pouring that money into your fleet is the best way to keep yourself well protected. If there's the threat that you'll wipe them out in a major battle, enemies will think twice about a brazen assault.
To deal with the AI's bombard assaults, the best approach is just four turrets. These, when placed right next to the planet (only need 2 for an asteroid) will cover against every angle of assault. You can also use scouts. These units are cheap and really fast and are actually quite effective at search and destroy against lightly armored targets like siege frigates. Hangers are kinda pricey and I generally avoid them unless I can make use of their special abilities (TEC flak turrets, Advent shield bestowal, and Vasari phasic traps, added in Entrenchment).
The best form of defense is proactive intelligence and keeping your fleet deployed effectively.