I assume that the OP is talking about the tournament and not just a "Hard" skirmish against the AI. I just played through the tournament on Hard difficulty as Erebus and found it to be an interesting challenge. I ultimately won, Sedna came in second, and QoT (yes, QoT) came in third. I lost about 2 sessions, at least one of which was slaughter (my allies just got farmed). The big thing is to do all of the things necessary to get a lot of favor points during each match. Killing Demigods is one way, but alone will not be enough. You also want to capture the most flags, get some assists, not die a lot, do as much damage as possible, take down buildings, and citadel upgrades. Even if you are on the losing team, you could still win the favor-point race, which is all that matters in the tournament. A lot depends on what demigod you are using and how the teams get shuffled up for each match.
While some will say that the skirmish AI is bad (it is actually a liability in most multiplayer games), I find that it actually performs inconsistently in single-player skirmish (at least on hard difficulty). That is, one game can be a great one in which the AI players don't feed a lot, gets some kills, upgrades nicely, and even appear to cooperate a bit with the player. The next game you might have AI Regulus die 5+ times or see some other foolishness. With the next 1.2 patch, the AI is suppose to be further improved, hopefully in a manner that makes it more reliably a decent ally and opponent. Right now, I think it probably has random builds and item purchases that cause it to be inconsistent from game to game.
