Hi!
A bit late, but it may help someone.
I usually play on "genius" AI level, but for this one mission I lowered it on intelligent, as Torians usually get insanely high econ out of nowhere (or at least I can't read the numbers from espionage).
This mission is IMO unballanced. Torians get tech advantage (Advanced Trade), that soon turns into econ advantage too (Galactic Stock Exchange IIRC), so in the first attempt I quit after seeing first torian battleships, while I've been struggling to research frigates.
My second attempt was driven with the thought "If they cheat so I'll do the same". I went with colonizers after yellow planets and repeated (reloaded) colonization until I got a PQ boosting event. Even that was not enough to match their econ, but then I noticed a purple sun below my homeworld sector. It had influence 100 and 4 planets PQ-12 and one PQ-13. So I reloaded a quite early savegame and went after those planets with the same "reload" tactics. It took me about half an hour to settle there, but then I got 5 more planets producing lots of money and influence. Even that was not enough to made torians' planets defect. I needed to invade one of their sistems to lower ther influence production. Therafter one had defected, but game ended because I won by dominating 90% of uni for 1 year.
IMO those higher # Altarian Prophecy missions are seriously unballanced for more than intelligent opponents, as they got too big advantages - lots and better planets close, more galactic resources, no minor civs to sell them tech to get more money, and, despite being a team, Altarians wanting warship tech for insanely high prices. (end rant)

BR, Iztok
~SDC~