Was honey in ancient times different than now?
It's not honey that's changed since ancient times, it's wine! Wine makers in ancient Rome lacked the knowledge and equipment to prevent oxidation and unwanted bacterial colonies, so their product was pretty awful by modern standards, being both sour and bitter with all sorts of off flavors. Honey and spices were added to try and make it palatable. 

So you can't re-create the roman recipe without roman style wine, which you won't find in any store because nobody would want to buy it! If you add the same amount of honey to wine of today it will be overwhelmingly sweet, my suggestion would be to add a little bit of honey to it and work your way up. I would also suggest you not follow the recipe to the letter:


Don't let it sit like the recipe suggests, add the spices in and let it steep, then strain and add more wine
Don't filter it through charcoal: the reason they did that was because wine makers added all sorts of awful stuff to preserve the wine, modern wines don't have those issues. If it has particulates try using a coffee filter instead.