It's a good idea for mods to declare all of their dependencies (in @ Mod) so that people not paying attention to the Curse metadata (cough, cough) aren't confused by random crash errors, and are instead greeted much earlier during startup with clear "X needs Y" error messages.

Looking at the source you seem to only depend on Forge itself. If you need an example, I guess tconstruct is as good as any...

The BaseMetals dependency is a valid complaint, the OreSpawn one is, IIRC, not. All of the various MMD "Metals" mods can use OreSpawn as an ore generator, but that can be turned off and other ore-generating mods can be used in their place.

In truth the BaseMetals dependency is set to go away when we finish the "MMDLib" base-code mod and get all the features in it stable and reliable. I don't know when this will happen.

As to anything else - any "plugin" that the *Metals family of mods have, internally, are only used if the optional mod dependency (such as TiCon) is available and the mod is active in-config.