if the devs got rid of the god supporting thing, where you can only support another city with myth units so long as they worship the same god, hydra's would be without a doubt the best cs escorts, the have = attack as an ls and nearly is as good as trimerines. apart from that the only + side with hydra's is they are unaffected by fireships. your enemy could have 1000 fireships and your hydra's would be unaffeacted by them. not sure if hydra's kill fireships though, but if they did that is another + on their half because you could kill 1000+ fire ships with a single hydra if that is the case.
its weakness is
1) to favour expensive
2) susceptible to sea storm and you will take more losses as in LS terms you will only lose them in bunches of 5 instead of maybe 1-4.
Hydra is invalid because it is not the most succesfull form of attacking. It is a mythical creature that only roamed the seas. Pick a better god to worship such as zeus.
hydra's are just as good for attacking as ls if not better because they are unaffected by fireships only difference is the hydra's are slower. shows you who the real idiot is aye.
I used them at the start of the game and found them to be effective but the time it takes to build them is definatly not worth it, better to build 2 ls nukes than the time it takes to build a hydra one.