When we play an epic battle event it is placed next to our plot deck until the end of the epic phase.

Is it counted to be in play? I'm not really sure if it is considered to be out of the play area. The wording says nothing and it doesn't seem to follow the normal rout of moribound-> leaving play cause we are told where we have to put the event, and it is not in the discard pile. If the epic battle is in play I guess it counts to our command, so now it is important to distinguish it.

I think Nate ruled regarding the deathbound epic battle that is is not considered to be in play when it is placed next to our plot deck, but I dont know the arguments to support this position.

I do not recall the exact arguments either (there's some wishy-washy hand waving when it comes to the deathbound unique epic battles), but I remember the same conclusion as you; epic battles are placed next to your house card as a "reminder", but are not actually in play in any actionable way.

The more persuasive ruling is that you can still use Bear Island in the dominance phase if you have an Epic Battle event by your plot card. With that ruling in mind, I think it's pretty safe to say the Epic Battle event is not in play, and therefore not part of the "at your command" count, either.