Any bug would be the guns. A ship bug would not affect shell damage in any way.
However, the DOE has far less gun space than the L2, and can only fit 2 binds with L2 guns. It would instead use the cloned ones from the Temeraire.
As far as the DOE is itself, it's a larger (aka: easier to hit) L2 with an option of slightly shorter ranged guns with (in theory) slightly more hitting power. That's it. Since the L2 already has BB6 supports, one of the main benefits of the tier is lost, and what's left would need to have something more interesting to be worthwhile.
IMHO, only the California, Thermidor, and Proletariot bring anything interesting to the table, and even those would only be recommended if you have tons of honor medals stockpiled with nothing better to spend them on.