Personally I would like to think the Dark Mirror being also the Twilight Mirror, but so far a few facts throws me off. The biggest one is the Dark World, and the OoT - MM - TP part of any Timeline.

1. The Sacred Realm became the Dark World when someone with an evil heart touched the Triforce, Ganondorf in OoT is the first Ganon in almost any decent timeline we know of that touches the Triforce first, and FSA has the Dark World so it has to come after OoT

2. In TP the Mirror of Twilight is broken, so if the Dark Mirror is also the Twilight Mirror, FSA would have to happen before TP.

3. Ganondorf from OoT and Ganon from FSA both comes from the Gerudos. Who, as a race, can only produce 1 male child every 100 years.

4. Ganondorf from OoT was capture and was unsuccessfully executed(which was when they then used the Twilight Mirror to send him away) shortly after the events of OoT.

If we add all this up(and try to keep the Dark Mirror being the Mirror of Twilight) we find that the Mirror of Twilight has been at the Arbiters Ground for at least the same day Ganondorf has been unsuccessfully executed, then would have been transported to the forest, where it would have to lay for at least about 100 years before the Ganon from FSA was old enough to go for the Trident off Power, so then the event of FSA would happen and at the end you gave the Dark Mirror to Zelda who sends it off to the desert just before the events of TP happened because TP happens 100 years after OoT...

yeah... I cant buy it, because this would also mean that the TP Link(or his nonexistent father) became famous right before TP for at least returning peace and defeating Vaati.