Fleets don't really have balance - they have purpose.

for instance the fleet you indicated:

120 LRF's, 50 light friggates, 20 carriers, 20 support cruisers and 5 capital ships

would be easily contered with

40 Heavy Cruisers, 70 carriers (35 fighters and 35 bombers), 20 support cruisers and 20 flak cruisers.

You see the LRF have advantage at a distance but only against other cruisers, the fighters and bombers will reach them before you can get to my fleet.  The 35 fighters will be able to keep your flighters grounded, if a few got out of the sceen they would get taken down by the flak cannons.  the bombers would focus fire on your cap ships one at a time while the heavy cruisers would make short work of your LRF.  the only chance you would have is to close distance as fast as possible.  But then again the HCs will close distance fast on your LRFs.  

I don't see there being a perfectly balanced fleet - the fleet configuration should be based on what you want it to do. for instance you would not want to field that kind of fleet against the Advent because of the guardians - they would simply shield up and whittle away at your forces.  I build fleets with purposes and based on what I need to counter.  If I want a fleet for hit and run tactics to cripple planets or trading,  I but 20 seige, 15 support, 20 flaks and 20 heavy.   IF a planet only have defenses and no fleet, this fleet should be able to get in detroy the population and get out mosty in tack and even more importantly do it fast.  the flaks keep off any fighters while the heavies take out the guns.  You see what I mean by purpose?  I find when I am being heavily attacked a good tactic is to send a small fleet like this to damage the enemies infrastucture a bit this will usually force them to back off.

Try different tactics, but find a purpose for your fleet. 

Technically, a balanced fleet is where all combat ships take up the same amount of fleet capacity (i.e., 2 LRFs= 1 HC); this doesn't apply to support cruisers.  However, in the real world, a balanced fleet is composed of counters to what the other player brings to the table.  There is also the discusion of early, mid, and late game.  In the late game, LRFs have much less of a purpose than they did early game because of their faility compared with HCs.  LRFs do jack against structures and anything else with heavy armor. 

Here's the problem as I see it, some support cruisers are pretty bad, and others are wonderful.  This has not been addressed, so a blanced fleet would be an odd thing. For example, overseers are really terrible at healing because their healing ability is forward facing, so the ship must turn to face target.  This just makes them really crappy at healing, and it's easier not to bother at all with them. 

Luckily subverters can pick up the slack because they are just that wonderful.  Why they wouldn't make overseers mroe viable I don't know?  Why doesn't a HC+Overseer fleet kick butt? I don't know. I mean I know why, because oversser abiltiy isn't 360 degrees, but why is it allowed to be liek this...

Same thing can be said about subjugators.  Really crappy at their subjugator ability.  The healing ability is so so, but once again it's the guardian that carries their fleet.  Subjugator heal ability will only save a cap ship some times.  It would not save a capship if there were no guardian and mothership present.  Subjugator ehal ability should be AOE targetting, and maybe not channeled. So they can dispense it quickly and go on to use domination ability.

On the other hand TEC have the best fleet composition because Ceilos are actually not that bad.  Though they do need micro management of their desigante target ability, otherwise they will target stuff no ships are shooting at.  But when used it can allow you to destroy enemy caps.  And their buff is useful enough and the autocast on it really doesn't have to work hard.  You cast it on any ship and it's good, it does it's job.  So that you never become angry with the autocast.

So for Vasari adding Overseers to their fleet has very marginal effect, same with Subjugators for Advent.  While adding either support cruiser to TEC fleet has a very big effect.

Okay guys, thanks for the help so far.

Dude, overseers are better than horoshikos.  Reason, they heal INSTANTLY and therefore they pretty much stack.  Horoshiko's repair over time, so it is possible to deal more damage than they can repair.  Not true with the overseer.  I still think the guardians are awesome, but overseers are probably the second best support ship and the one that is used the least.

20 seconds to turn?  Wow, you computer must suck.  Even without micro managing them, that's unheard of.  Here's the secret to using the overseer:

1. Click on all of your overseers and turn auto-attack to OFF.
2. When in a battle, have your overseers move somewhere where your fleet is, having them on the edge of the gravity well is a no-no.
3. If your cap is getting mircoed, click on each one and tell it to heal.
4. Watch as your cap survives forever and the enemy pulls out his hair.
5. Laugh as you slaughter his HW and rape the women.