The trick to playing harder AIs is recognizing that they can easily get stuck on choke points and beefed up static defenses. They don't avoid these like humans do. Because of this, putting a starbase at a gravity well that bottlenecks to the rest of your empire and then buying the health upgrades for that starbase, you can buy yourself a ton of time to build up huge, teched up fleets of your own. Then, after the AI wastes an armada against your damage-soaking starbase, you can strike back at a time of your choosing.

What are you building for fleets?

To answer your question, I am building fleets that I guess will keep-up a good fight. I have noticed at times that I have too many cap ships, but then again on another front I may only have 1 cap and the AI comes-in with 4 caps against me! AAAaaarrrrgggghhhhhhhh! Sooo frustrating.

All told, I think I am buididing a balanced fleet. To boil-it down, I guess I can make my observations:

   Seems I lose all my light frigates sooner than the opposition.

   Seems the AI comes in with more cap ships than I have as well as more heavies.

   Seems I got to have some plan or tactic, overall for this, but keeps getting SQUASHED!

This is a good idea if the pirates are on and for unlocked teams, but otherwise they're pretty useless. Relations determine who gets bounty on them but the AI won't go half way across the solar system just to attack the enemy they hate the most.

Light frigates are probably best kept to a minimum. Unless your enemy has a lot of carrier cruisers or repair cruisers don't have more than 5, maybe 10 for maxed out fleet supply. Are you playing trinity or Rebellion? Regardless the mention LRF and bombers do very well against capitalship, and once you a mass a lot of bombers (50+ squads) the AI can't really compete with you.

If you've got choke worlds that they're attacking you on but don't have Starbases unlocked yet, repair platforms and hangars are cheaper and also helpful. Advent hangers can be upgraded to give their other defenses shields, which massively boosts the durability of all their static defenses (and it even gives a close enough Starbase a shield boost!).

Or if you just have to throw them up quickly while your fleet is defending, a couple of Repair Platforms can help.

Culture can also help if you've got time to get it going, because you seem to be stuck on the defensive so you'll be getting the bonuses. If you can get past that initial big AI assault you'll probably gain some cap ship levels and get time to set up more defenses. At that point it's pretty easy to go on the offense.

What race are you playing as?

They are designed to go against such frigates yes. They have anti-Heavy weapons and Carrier and Repair Cruisers have heavy armor. You are also correct that their short range is an issue as Long Range Frigates are good against Light Frigates and cause them to melt.

Diplomacy's AI is harder so learn now.

Tridus, I have been mostly playing as TEC... feeling my way thru and mostly have a good feel for the TEC tech tree in Entrenchment.

 I get a lot of advice to "built trade ports" fast... and have been doing so. I find that putting-up 2 civ. labs and the cash to research Trade Ports takes aybe 10 min of game-time and in that time I have done zero military research like lasers, etc.  

What is the sweet spot against 2 hard AI? It seems they always build powerful fleets right at my border and pounce me before I can really get-up strong defense... Of course if you read and understand exactly what I am talking about then you have been through this!  Is there a good answer? What is the best path in the tech tree(s) and how far does one extend territory and build barricaded planets?

Sorry to sound like I expect some magic formula for all situations, but I feel asking this presents such excellent replies about strategy I can't resist!

Thanks and Live Long and Prosper!

I usually tech hard to Star Bases before putting up an economy.