Iconius Guardian and Domina Subjugator

Iconus:
1. I think what you saw was someone using the word "micro" meaning micromanagement. Meaning you need to pick 3 Guardians and tell them to activate the ability.
2. The damage shared buff is not stackable, so 3 Guardians do not provide 99% damage shared. There really is no maximum benefit once you start talking about respectable numbers of Guardians.
4. Use Repulsion to exclude all ships except for strike craft and long range frigates from the battle (its a good way to protect your long range frigs from enemy heavy cruisers).

Domina:
1. Its healing ability (in my opinion, at least) wasn't meant to be spammed (40 second duration, 60 second cooldown). Yes, it does recover 1000 hull points when its done, but its real benefit is preventing the ship being persevered from being disabled (that is, Ion Bolt, Reverie, and Distortion Field do not work on those ships).
2. Suppression is good for keeping heavy hitting ships out of the fight and stop certain frigates from phase jumping.

Guardian

1. Not really, though you could form a fleet of your guardians so you can use a hot key to select them, and then just hit the button.

2. Each ship can only have one guardian shield buff at a time. However, multiple guardians will cover eachother, allowing they to take some of the damage for the first gaurdian. However, you'd need to be in a massive battle to ever need more than three at once.

3. A fleet with about 1000 fleet points can fit inside a guardians area if you keep them really close together. Mainly used too make the "battle ball" where illuminators cluster around a gaurdian(s) with a mothership nearby.

4. Often a good choice, though repulsion field is one of the best ways to protect carriers and to stop the rare Heavy cruiser spam.

Subjugator

1. Infinite Void nailed it. I try to keep one for every cap ship I have. Not worth using on frigates, save maybe carriers.

2. Depends on what kind of enemies you are fighting.

Suppression from the Dominas is an incredibly good way of pinning down enemy carriers that will try to kite your fleet around the grav well. 

Guardians are funny ships. 2 shield bubbles at once does everything you need but i always include 5 or 6 Guardians in the fleet. because they die first. the others are literally just their replacements, which i consider important enough to build in advance and take along with the fleet until they become necessary. waiting for reinforcements on these ships is unacceptable. they're the heart and soul of the advent fleet (combined with the Mothership anyway). 

Leaving Perseverance on autocast usually has these outcomes:
1. Subjugator perseveres a capital ship
2. Subjugator perseveres another Subjugator
3. Subjugator perseveres a frigate (usually Iconus Guardians, but I've also seen them persevere flaks)

The first outcome is the most preferable result, but they persevere other Subjugators just as frequently. They usually get to using it on frigates when they run out of capitals to use it on.

Iconus Guardians:  Take one or two off auto cast and hot key them.  In a fierce battle they become your back up IG!

did they nerf the repulsion ability, btw?  it doesn't seem to be quite the bitch-slap it used to be...

If you haven't played sins for a while, yeah they nerfed it. It was a little while back though.

It was not a little nerf, it was huge. 

But anyway, subjugator is hard to use effectively.  It needs micro mostly for the healing ability.  The other abiltiy can work if you put the ship on hold position, though it may still move a bit out of formation when it tries to cast it.  Idea behind it is to stop few ships that get through the repel.  It is most useful on a Heavy Cruiser.  The healing ability will remove disabling effects as well.

I love the Gaurdians but I don't get the replusion ability,  it sucks now.  It is useless and doesn't help me at all.  Their shield is amazing and rivals the Hoshiko even.  I would rather even save the Anti-matter for another round of the shield.  They increase the survival of near by units by a lot.

Repulsion isn't as good as it used to be but its still very effective for certain circumstances. in particular its great at keeping short ranged attackers like light frigates or heavy cruisers away from your battle-ball, which is filled with ships like Carriers and support cruisers that are, interesingly enough, very weak to light frigates and heavy cruisers.

its not as important an ability as it used to be but its still very good at punishing fleets of heavy cruisers. definitely worthwhile in my opinion.

I still get a chuckle at putting guardians 'behind' a 'jump in' point and shoving the new arivals into a cobination of mines/static defences/ships.