First of all, TTK_GeneralNoob, mythic age Greek heroes only cost 4 pop, not 5.
Second of all, yes Toxotes only have 13 attack (if you round things up you MAY get something close to 14 attack - I don't know).
Third, no one in their right mind would make an army of all Gastraphetes. Gastraphetes are more of a back - up unit as they are too expensive to mass.
Fourth, FU Gastraphetes with burning pitch did around 50 damage to an unupgraded wonder. Sure, that's not as much damage as Helepolis or Petrolobus, but it is sure enough to seriously damage buildings. On top of that, they are effective against human soldiers and even myth units.
You can't compare the Gastraphetes to other units that specialize in one area. The strength of the Gastraphete is their power against a number of different units. Helepoli are pretty terrible at human soldiers and myth units, unlike the Gastraphetes from behind a meat sheild.
And concerning hard infantry counters, which do hack attack:
Most infantry have at least 50% hack armor FU, and most hard infantry counters, like Hypaspist, have around 8 attack and x4.25 bonus against infantry. If you negate the 34 damage by the 50% armor, you get about 17 damage to the enemy infantry. Gastraphetes do about 32 peirce attack FU verses infantry (because they fire about once every two seconds, thus double the attack), which, negated by the average infantry peirce armor FU (about 35%) you get about 21 damage to the enemy infantry.
So basically, Gastraphetes do more damage, and have the advantage of long range (but then you have to factor in the cost). I agree that they are not the best unit against either buildings, human soldiers, or myth units, but they certainly are a unit that can do well against any of them given proper usage. And that is where their strength, IMO, lies.
~~ Strider s~~
There is a time for many words, and there is also a time for sleep. - Homer