I just defeated it on my level 51 Swashbuckler so here are a few tips for the fight

1. Your line up should consist of a power hitter, a sponge, and an anti musketeer.
I used Sarah Steele, Holkun Doomhorn, and Nausica

2. The Power attacker will work on clearing the redcoats one by one
3. The damage absorber (Buccaneers are wonderful for this role) will go in and make the redcoats attack him and not others (Also a pet could help absorb a little bit of damage as well but mine didn't join when I did it sadly)
4. Your Anti Musketeer which is basically a companion that does very well against musketeers which is very useful in this fight (except the 2nd wave has one swashbuckler hence why I picked Sarah for my power attacker)

5. The third and final wave will have a couple redcoats and that little short captain guy (forgot name but since he looks like Handsome Dan, I will just call him Dan). Hopefully your companions survived but even without them you can still do great. You only need to beat Dan so use your hide powers to buy some time (and maybe use a few healing powers) and when your ready ATTACK DAN! You can deal tons of damage via your multiple first strikes along with your Stab powers. (especially if you use a stab power while invisible) Dan may miss you as well adding an extra hit in via reposte. If any companion survives then focus all there moves at Dan to make short work of him.

6. Try not to waste ANY powers in the first few waves

I did this a couple days after marlybone was made I made it out with 12 health as a witchdoctor to me this battle is OP I mean 3 waves of 4 redcoats with 1800 health when my companions at 50.

If ya struggle with the battle, get some friends. Luckily, I breezed through the waves and got myself a redcoat outfit :D