You can stop crying now KerrekCruiser, I gave you some Karma.
I would have thought that Advent are best in the mid/end game when you get to the killer combo of guardians and Daestras, but I've only played one game vs a Human, so I'm probably wrong.
[Open Question] What sort of fleet makeup do you go for in the early game/mid game/end game
I normally take a Progenitor with colonise and malice +6 or so disciples. As I get the tech, I add 1 drone host and then up to 10 illuminators
For mid/end game I usually take Crusaders, Guardians, Illuminators, between 3 and 6 carriers, 10-15 disciples and a number of defenders.
Precise makeup is determined by enemy fleet makeup. So if they're using a lot of bombers, I'll add more disciples (to kill the carriers), fighters (to kill the bombers) and defenders. If they use a lot of heavies/cap-ships I'll take a bunch more daestras.
I don't really use domina subjucators, their abilities are, frankly, second rate. (IMHO)
As for Guardians, I can't stress how good these are enough. They can protect your ships really well, *and* they can be used to great effectiveness to disrupt enemy formations with repulse. Seperate the support from the rest of the fleet if you can, if not, just spread their ships right out, it'll reduce the efficiency of their AoE abilities, waste their time if the ships attempt to reform formation and it also allows your illuminator swarm to make full use of their side lasers.
Disclaimer: I'm not very good yet, these are just my views on what works.
Also: bring cap ships, Fleets without cap ships perform much worse than expected.