I figure James would've been there, despite his lack of arm, though he would've warn heavy cloaks and a mask in an effort to disguise himself. He probably nearly splinched himself thanks to the wards, but caught it in time, apparated back to the safehouse, and then apparated again quickly to a short distance away and walked in. He would have torn at the wards with whatever magic he could muster (which he helped take down, certainly, but I'm not about to claim all the credit his, lol, so I'm sure plenty of other people had a part) and probably did a fair amount of shouting to try and get Sirius' attention, to no avail.
As soon as the wards came down, James would've torn in fast and sworn a whole hell of a lot at Edgar's state. He wouldn't have hesitated a split second before wrapping his arm around Ed's shoulders and apparating them in a kneeling position back to Ed's house. (Brused the fuck out of his knees doing that, but he's not about to complain given the state Ed's in.) Then, if no one else did it on instinct, he'd have sent a patronus to Dig with the apparation co-ordinates and the words "Come now". He probably would've tried a few blood staunching charms, but he wouldn't have wanted to mess anything up for Dig so he'd have mostly tried to find a pulse and get himself covered in blood.
Dig knew about the fight, but did not go. He was a healer, not a fighter. He had spent a few hours that evening tense as hell because he didn't know if that night he'd be trying to pull someone else back from the brink of death (again!) over what he thought was a terribly idiotic plan. Eventually Veronica got sick of his nerves, and a shoulder rub turned into slowly removed clothing. They were in bed when the patronus came, and Dig put on a pair of trousers and apparated as he was pulling on a tee-shirt.
He all but pushed James out of the way (now was not the time for niceties) and started barking orders. Blood replenishing potion, anything to staunch the blood flow, as many hands putting pressure on the cuts, preferably those close to him only as (sorry Ed) Dig got the clothes out of the way of his healing. Between the burns and the cuts, Dig had to cut some corners to get Ed under control quickly, and would basically have had to cast, uh, whatever sort of spell basically works as the equivalent of shock paddles since Ed seems close enough to death that his heart might stop a few times.
In the end, after working on Ed for a while, Dig would've used potions or spells or a mix of the two to put him in a coma, of sorts, so he could heal and he would not have promised anyone a positive outcome. If anyone asked him if Ed was going to be okay, Dig would have just said, "The odds are not in his favour." Or something else similarly grim. He would've stuck around for a few more hours working with charms and such to counteract the dark magic, since most of his other work had just been to get him to stop bleeding.
Uh, so I rambled. But I think that about covers it? Does that work?