Ah, time for some foul magics.. Yes, I'm talking about necro-threading
Anyhow, just finished a game playing with the Byzantines, and what a wonderfull civ it is. And their UU might be one of the only that can be used THE WHOLE GAME LONG! Most people might think that keeping those old tubs alive is a waste of money (upkeep), and that these firespitting antiques can't hold up the race from the moment the first Ironclads appear.
Granted, on a 1-vs-1, the Dromon will certainly loose against the Ironclad, but if you get in such a situation, your strategy as poor as it gets.
By the time the first Ironclad gets launched, you should have quite the armada of Dromons. They should be sailing the seas in troops of minimum 5 each. If you encounter one of these "superior" ships, approach it and BOMBARD. Chances are, by the time the 4th Dromon has released its lethal stream of fire, that rusty tub they call an Ironclad is doing some deep-sea exploration

And honestly, any other ship -even the mighty battleship- has a hard time countering this tactic. Lethal sea-bombardment is a bit of a gamebreaker, if used correctly
Now, even if its land-bombardment is non-lethal, it is far from useless. But again, one has to know how to use it. Your Dromons literally stink if you want to use them as a means for sabotaging land improvements. Also you won't come anywhere close to destroying a city-improvement with your UU. But, an 8-stack of Dromons can severly cripple a defending force in a city. And again, ranging from the humble Spearman to the mighty MechInf, everybody fears the onslaught of an endless stream of fire. True, you'll first have to burn your way through any navy harboured in the target city before you can begin roasting those defenders, but the smell of a fresh woodfire will only sharpen your appetite for the barbeque which will follow.
And this brings me to the second great trait of the Dromon, TRANSPORT. Oh yeah, I can hear you already..."We all know the that a dromon is a transport, quit stating the obvious!". But what you have to take into account is this: the Dromon is a BOMBARDING TRANSPORT! Let us go back to the previous 8-stack of Dromons. If you know how to plan, than that 8-stack will not just be giving fire support, but it will also carry troops into battle. 16 units, to be exact. Chances are big that you can redline almost all defenders in the target city, which will diminish the chances of one of your attacking units falling during the actual invasion. And it might be a weird sight to see Tanks rolling out of a Dromon, but the element of surprise is always a boon to any invader
So, in conclusion... The Dromon, eventhough depicted as a wooden ship and powered by slaves who are tugging their years away at the oars, is a UU that will continue his usefull life throughout history. In its first days, it's the terror of the seas, unequalled by none. When Magnetism comes in play - thus ending the possiblility to produce them- they become the Frigate's little brother. And as soon as Combustion arrives, I like to see them as Gunboats: little versatile coast-huggers
