Help against the AI

Well carriers are a bit tricky, as you have to choose between suppressing the fighters or destroying the carriers themselves. If your defending as the Vasari, you actually have the best weapon to do this, the phasic trap upgrade for your hangar defense structures. This ability will freeze any amount of strikecraft in range, making them unable to attack, essentially making his twenty carriers useless. For any other frigates/cruisers Vasari subverters are a great for crowd control, as they can disable clusters of nearby ships.

Your right to be suspicious of static defenses, but starbases can be of worth if the planet is worth defending and if you use them right. The Vasari starbase is fairly unique as far as starbases go. Its not as good of a defense as the other races but it can move. Also the vast majority of its firepower comes from the second weapon upgrade (the first one is best against structures but it adds damage to ships as well), which gives it phase missiles (by far the best weapon type in the game, provided you've done some of the research). Its defenseless against strikecraft though, another reason Vasari hangars are popular.

As for the capital ships, a large number of assailants or bombers (both with upgraded phase missiles) are most effective. Otherwise a Kortal (disruptive strikes) or Evacuator (Nano disassembler) have potent anticapitalship abilities. An upgraded Vasari turret can also stop "Passive Regeneration" on capital ships, which prevents them from automatically regenerating hull, shields and most importantly antimatter for a while.

If we're talking about capital ships level 5+, then it's very likely that we're over an hour into the game.  With a normal difficulty AI, possibly as far as two hours.  Basically, by this point, anything goes.  I've heard of people achieving over 600 credits per second income within two hours.  The bottom line is that if the enemy fleet is considerably larger than your's, the answer probably lies 30-60 minutes in the past (or even longer) when they built up a superior economy to support it.

Hangers with phasic traps.  Don't build any strike craft, and save all your antimatter for this one ability.  This will completely shut down huge quantities of their strike craft and render them easy prey to your units.  As Vasari you don't have a great unit for chasing carriers (in theory it's the Skirmisher, but it kinda sucks) but against the AI you should have no problem making due with Assailants.

Make sure to bulk up on phase missile research, this can really boost your damage a lot.

Starbases deal fine damage; I don't know what your issue is here.  The first attack upgrade for the Orkulus is actually not as bad as it first sounds.  It may deal less damage than the other weapons, but it attacks fewer targets meaning this damage doesn't get spread out over the enemy fleet (which can make it easier to absorb).  The best damage-upgrade for the Orkulus is its second, however.  Phase missiles are absolutely awesome weapons once upgraded, and their base damage is rock solid to begin with.

Use repair platforms to boost your defensive longevity.  Static defenses can be a downright pain to take down with a good formation.  They're no substitute for fleet, but against the inflexible AI they will easily handle any direct assault it might throw at you.

The upgraded turrets and hangar defenses sound great.  I will definitely try these.  This sounds to good to be true.  I will be probably asking for a counter to these next week! 

I didn't realize a second weapons upgrade on the starbase would be different from the first one, so I didn't even bother getting the first one.  The second weapons upgrade sounds like it has potential as well.  Any advice on which defensive starbases upgrades are worthwhile (shields/hull/armor, frontal shield, debris repair, etc.)?  It seems like right now I am partial to the shields/hull/armor because of the synergy with repair platforms...

600 credits per second sounds incredible.  Is there a guideline for what your fleet supply should be relative to your income (i.e.- don't drop below 20 credits/5 metal/5 crystal after taking out fleet supply reduction?).  I would ask if there is a guideline for income relative to time played, but that seems like it would be affected by the size of the map and number of players more than the previous question. 

Thanks to all of the replies.

The turret has range issues, but the AI isn't smart enough to keep its distance against these kinds of static threats.  Really this is more a case of the AI walking into a death-trap than the turret being very strong.  In multiplayer, using turrets is very difficult even with these powerful upgrades.  The hanger, on the other hand is too good to be true and widely regarded as one of the most overpowered effects in the game.

All good.  You generally want at least 1-2 of the hull upgrade to give your starbase staying power, then one or the other of frontal shields or debris vortex.

Unfortunately no.  The biggest problem is casualties, which are extremely variable.  If you're taking large quantities of casualties, your fleet size needs to be kept smaller (since you have to expend more money to maintain it).  On the other hand, if you're taking very few casualties, you can reach absolutely massive fleets on next to no income.  I've personally hit 1000 command on less than 20 credits per second.

Those super-massive incomes are typical of large team games where one player begins surrounded by allies.  In this situation (typically called the "pocket") that player will forgo fleet entirely and spend all his efforts on building a super-power economy, then using his income to "feed" his allies.  This specialization can build economies that are completely unattainable otherwise, and greatly improve a team's overall position.

Yep, seen it happen before when I was a total newb and got roflwafflepwnd. The usual setup now for those econoboom strategies is highly noticeable at game start since you will usually have 1 TEC member (economizer) and 2 Vasari members. Best counter is a level 5+ Rapture with focus on Concentration Aura and 10+ carriers roll through the econoboomers territory and microing the bombers to attack trade ports and refineries. This is mostly a diversionary tactic since he will then call in an ally from the front line to protect their investments and you just need to kite the backup fleet as long as you can while your team focuses on trying to spread the enemies forces and take a planet or two.