Actually, I don't beleive Greeks have such bad heros. I think Greeks do have a pretty easy time versus a titan, as compared to Norse. Greeks get a ranged hero, Classical age, while Norse don't. If anyone needs another hero unit, its the norse, specially Loki, since he doesn't get Ragnarok, and the Titan can pull the Nidhogg down from the sky like paper (lol).
I myself am a Greek player mostly, Hades. Hades isn't bad at all. Toxotes massed are very powerful, backed up by a couple hoplites in classical, then proms once in heroic. Add some cyclops, you've got a great army, cyclops as the building killer, toxotes and proms as the backup units. Hades can concentrate on archers, leaving him lots of food to make his eco with, and save up for advancing, and for armory techs to improve hack armor.
Greeks are fine, it's all about how too play them. Make lots of vills, take advantage of the variety of units. And Greek Heros own. Combined with beast slayer, Greeks should have no trouble with mus and titans.