Hi KO, welcome back!
I don't think Ashdod is more powerful.
Like Baalz said hinnom has some super specials like posibility to cast all site searching spells other than water. And this is really important! Ashdod miss blood, nature and air in addition to water.
Blood Magic is a powerhouse and ashdod doesn't have access to it. Its even possible for hinnom to produce blood stones.
On the other side you got things like +15% Forge Bonus which isn't that good. With dwarven hammers (you normally have when producing items and ashdod has easy access to them) you got only a marginal bonus for the low cost items. 5 gems items cost 3 in both cases, 10 gem items cost you 6 instead of 7 so you save 1 gem. In higher costs the bonus is more worth but the main items you produce are at 5/10 gems (pendant, amulet of am, brands, most used armors and shield, etc.).
Well you don't have people killing giants but it doens't hurt hinnom much atm.
Btw, the possbile build of Ammi (and ashdod raphaite sage) without any lab is because of the bug that every mage with only random magic doesn't need a lab. Its also an advantage for this nations. Maybe you can fix it