It is 'hard' on hard, I think perhaps unfairly so - for example, some opponants seem to have 3/4 capital ships very early, along with a fleet of lesser ships!
I have medium nailed as far a winning tactic are concerned, so I thought Id try hard - I got squished big time. I tried again, this time just pumping out ships to beef up the fleet, ignoring the more rewarding (to me) tech trees - this worked much better, but a lot less fun, and certainly too frantic (from a RTW lovers' perspective)
In the end, I compromised, and set two thirds of the nine AI players to hard difficulty, and the rest on normal. This turned out to be a lot more balanced, and after a few days, I won last night (7Deadly Sins Mod) I played as TEC, having the colonise CS first, followed buy Colbolts, and teching them up for lasers, shields and the disable enemy power core tech. I then get the Marzda Dreadnought (I have found this is one of the strongest, after constantly losing the Kol CP's to enemy fire) I then focus on getting the 5 military structures for the Kodiak cruiser - once you have this, you really do have a fighting chance - even more so on hard (the Enforcer is you're playing as Vasari is more or less the same)
I then try and scount for ship graveyards and make half a dozen colony frigates, these derelict ships are a fantastic idea, and really do help beef up your fleet, or leave them orbiting one of your frontline planets.
Later in the game, I found it's best to use up all tactical slots for the planets, as at the very least, it will take an enemy force a lot longer to take your planet, and give you more than enough time to send reinforcments.
Overall though, hard is, I think, just a little too hard, and a huge jump from medium, from my point of view at least.