Looks pitted to me, too. 10 minutes w/ soapy water and a brush should have removed all traces of powder fouling. May be a classic case of "shot it and forgot to clean it last year".
You really can't judge the damage until you shoot some groups. A little pitting is not necessarily the disaster in a ML that it is in a centerfire. In a centerfire, copper jacket material builds up fast in the pits, and the fast velocities rip the bullet jackets. The accuracy problems associated with pitting are due to the damaged bullets. If you're shooting sabots, your bullet will not be damaged by bore pitting, since the bullet doesn't ever touch the barrel...only the sabot does.
But you will pick up plastic fouling and increased powder residue fouling, which will make that second shot harder to load, and you may see a loss of accuracy as the plastic fouling increases over the shot string (hot water won't remove the plastic fouling...you'll need to clean that out w/ something like Hoppes...like cleaning a shotgun barrel).
JB's is good stuff, but I've only used it to remove extreme copper fouling in centerfires. It's not designed to remove barrel material, and there's a real possibility that you'll damage the barrel crown if you start running the rod in and out, over and over, trying to "polish" the barrel.
If it was me, I would shoot the thing just like you always do and see how it does. It's going to be harder to clean from now on, but it may not shoot any differently that it always has.