Vasari Loyalist death fleet is definitely the most fun I've ever had against the Sins AI. For those that don't know, "death fleet" is when you rush "Strip to the core", build your titan and then cannibalize your capital, as well as any of the dwarfs and asteroids you colonized up to that point. After that, you are a Battlestar Galactica type migrant fleet.
The goal of the game at that point becomes taking planets as you need them, so that you can replenish your fleet. You then strip the planet and move on. Meanwhile, the AI rips itself to shreds, and/or sicks pirates on you constantly (which is an experience grinder for you, since you are at that point essentially invulnerable against pirates) Anyway, here's a few tips I've picked up, for what they're worth:
1. Research Highly Attuned Sensors. As a mobile empire, you need to know where your enemies are concentrating their power at all times. With knowledge of their fleet movements, you can discern where their weak planets are. Additionally, you can see the HPs of any high priority targets, such as titans, whenever they enter phase space. I often see a weak titan running from a losing battle..this is a great time to pick them off. Sure, they can run from you, but you can chase them with your entire fleet. Also keep in mind that the VL Titan has an ability that lets it close with a fleeing enemy immediately.
2. if you set all the AIs against each other and lock teams, the game will probably be too easy. I like to set everyone against each other except for 1 team of 2 AIs...and I like to make one of the solo AIs "Unfair." I set all other AIs to "Hard." Pretty fun.It usually results in 2-3 super powers that can be very difficult to crack in the late game.
3. Each time you capture a large planet, make sure that you think ahead when deciding which ships to build. You need planetary bombers, anti-strike craft and support in your fleet, not just heavy frigates. The game can become quite difficult at times, and you may find yourself going a stretch without a frigate factory. Plan accordingly.
4. Don't rush to build 16 capital ships. You don't need that many till very late game, and it will utterly destroy any credit income you may have. Build a few capital ships every time you take a terran, ice or volcanic planet.
5. Kind of goes without saying, but don't EVER let your Titan die, especially in the late game. Building another will usually mean gobbling a large planet, and by late game, these will be well defended and supplied.
6.Vorastra; set Micro-Phase Jump to manual. The AI wastes it. Upgrade its systems too, don't just focus on abilities.
7. Keep at least 55 Ravastra Skirmishers in your fleet at all times. In fact, if you only ever build one frigate, let it be the Ravastra. Its a tough little ship, much stronger than its counterparts, and it has a nice HP regen upgrade. Without doubt, the Ravastra should be the backbone of your fleet. I don't even use Enforcers in most games. If I do, they only serve as damage sponges for assaulting TEC space stations.
8. Be a general! Don't let the AI assign and prioritize targets for you. It does a horrible job. You need to direct your fleet in combat. Don't do so by clicking on the ships as they fight in the grav well. Select and manipulate them from the menu on the left-hand side of the screen. It's just more efficient. Use "Alt+click" to select all of a certain type, and then have them attack the units they are designed to attack.
For instance, tell your bombers which targets to attack. They don't know which targets are highest priority, you have to tell them.
9. Focus fire on capital ships and carriers as soon as they come in. Destroy capital ships one by one, don't worry about frigates. Generally kill in this order: capital ships->carriers->heavy frigates-> light frigates. This is the way to go if you're playing against AI. Send your bombers to destroy carriers as soon as the appear.
10. If you're sitting in an grav well with your entire fleet, don't panic when you get invaded by the AI. If you own the planet, build a phase inhibitor and use the grav well as an experience grinder. With a titan, at least 9 cap ships, 50+ Ravastras and some anti strike craft and a support wing you should be invulnerable to all but the strongest fleets. Of course, if an enemy Titan joins the frey, you might just want to gobble the planet and run.
11. Once you break through an AIs outer planets and get to the soft inner belly of their empire, you may want to set up an economy there. To do this, preserve two large planets, colonize and then fully upgrade their logistics slots. (make sure to upgrade civic infrastructure as well, so you aren't running in the red) Then simply build 4 trading stations on each planet. With space gates you can defend these economy planets reasonably well, as long as you are in the same system.
12. Maintain at least 20 bomber squadrons in our fleet. Don't bother with fighters.
13.Keep in mind that draining a large planet results in it becoming a dead asteroid, which other empires can still colonize. They don't get any logistic or tactical slots, but they can still use the resource asteroids. For this reason, its best to re-colonize and strip the dead asteroid down to an asteroid field. You won't get anything, but you'll rob the enemy of the chance to use the resource asteroids. This is how you win, by slowly sucking your enemy dry.
14. If you are attacking a planet that you know has a star base on it, set the movement to fleet wide simultaneous jump. You don't want your frigates jumping in 30 seconds before your titan gets there...they'll be destroyed pretty quickly.
15. Be very careful when attacking a TEC Loyalist star base. Their "red button" ability means that they can wipe out a lot of your fleet. By all means use your Ravastras and your bombers to soften up the star base, but manually move your frigates out of range when the station gets low on HPs. If the bombers get hit by the shock wave, it only costs you antimatter. Losing your Ravastra wing can mean the game if you can't resupply easily.
16. Want easy cap ship upgrades? Send a couple of scout ships into a pirate grav well. Once the pirates give chase, have your bombers, cap ships and titan go to work on the defenses. have your Ravastras focus fire on the most powerful pirate frigates. Once the stationary defenses are destroyed, you can destroy all of the pirate frigates with ease. Once you completely destroy the pirate base, the choke point will be opened up to all other factions. The gravity well will become a super highway for the various factions, and they will take pot shots at one another in passing. Your fleet can just chill there, mopping up the weakened ships as they flow in and out.
17. It is a mistake to eat every planet you come across. Doing so will give you big problems in the late game, since you will eventually find it difficult to take the remaining planets..the will be heavily fortified.
18. The VL super weapon now requires you to own 4 planets before you can use it, but its well worth it. You SHOULD make at least 2 pairs of econ planets anyway, in late game. You'll need the income. The cannon heralds the arrival of your fleet in a big way, and gives you, the invader, a big tactical advantage. Namely it prevents all tactical and logistical structures from acting for a few minutes, and it deals some damage to boot.
19. I suspect this may change in a future patch, but for now, you don't have to be present in a gravity well when you are stripping it. Use this to your advantage! Once you hit the "scuttle" button, get out of dodge. If your planet has low HP, you might want to leave a few frigates to destroy enemy planetary bombers, but you can safely ignore/avoid all other types of frigates at that point.
20. Avoid going head-to-head with another Titan unless its unsupported, severely damaged already or yours is several levels above it. In most cases, the damage that your fleet will take just isn't worth it.
21. In late game, when you have a few allies, you can set up a Titan gank by telling your friends to attack a gravity well that you know an enemy titan to be in. they don't always get there in time, but when they do, the extra damage sponges can mean an easy Titan kill. Sometimes getting them all in the same gravity well just comes down to pinging multiple star systems that you know the Titan to patrol and getting lucky.
Once you get it right, just wait for the enemy titan to engage an ally cap ship, and then use the mini-phase jump ability to close with it from behind. Make sure the Vorastra will be facing it, and don't jump in too close. The weapons need a certain range to be met before they'll fire. Focus fire with your bomber wing, and when your fleet catches up, finish the Titan off with fleet-wide focus fire.
Well, I think that's all the tips I have for now..These tips are for new players, obviously 
