Beign the fenerals of Sauron im sure that atleast a few if not all of the nazgul were present. Atleast they would hurry as soon as the reports of the approach of an army would reach them.

As for the bodies in the dead marshes I can only guess One might think that the the army of the west was so vast that the flank of the battle could've easily reached the dead marshes or perhaps the first battle of the coming siege was fought there.

As for other leaders I would say that atleast the sons of elrond and the sons of elendil deserve mentioning.

as for Sauron not beign there I only found this passage from the encyclopedia of Arda: "The Battle took place on a wide and dusty plain before the entrance to Mordor, and many who took part were lost in the marshes that bordered the battlefield on the west. There was great loss on either side, but Sauron was defeated and fled back to Barad-dür. After the Battle was won came another seven long and bitter years of siege"

The above of cource implying that he actually was there.

There is actually more than one battle, that took place on Dagorlad. I assume you are refering the one which was part of the March of the Last Alliance (a.k.a. the War of the Last Alliance). This battle took place around year 3434 of the Second Age.

DAGORLAD (meaning the Battle Valley [Sindarin word, possible etymology: dago=slay; dagor=battle; lad=valey])

Geographically Dagorlad was laying into North-West of Mordor and so it was the straight way to chose for any large army heading towards the Black Gate of Mordor.

About the battle fought between the armies of the Last Alliance and the armies of Mordor I found this information (hope you'll make it useful to your purposes and goal):

The armies of the Last Alliance consisted from forces of diferent races gathered under one banner against the threat of Sauron. There were the Eldar (Elves) under Gil-Galad's command. Then there were the Dunedain under the leadership of Elendil. The Dwarves were presented by an army led by Durin IV. The Host crossed the Misty Mountains and was aided by forces from Khazad-doom, Lothlorien and Eryn Lassgallen (later known as Mirkwood). We can assume their leaders joined the Host too, so Oropher (King of Eryn Lassgallen, Sylvan Elf) and Amdir (King of Lorien, Sinda) can be placed there also.

Oropher died during the first stage of the Battle of Dagorlad, while fighting the Orcs of Mordor.

For the Enemy fought also men: Black Numenrian, Haradrim and some Easterlings.

The Alliance suffered great casualties and had to bury them along with the slain enemies in the flooded fields, that became to be known thereafter as the Dead Marshes.

More about the Battle itself you can find here: http://tolkiengateway.net/wiki/War_of_the_Last_Alliance#The_Battle_of_Dagorlad

                                        courtesy of: TolkienGateway.net

As Arath already pointed there were the Sons of Elendil (Isildur and Anarion). Later by the seven years of siege of Barad-Dur Anarion was eventually slain and after Sauron came out his fortress and killed king Elendil, Isildur remained only heir of throne for both Kingdoms of Exile (Arnor and Gondor).