I'm guessing the '10 is similar to the '09 in this area as I have an '09 and the lower headstock has 4 wires connected via two terminals. These are identified on the schematics as Ground 4 and Ground 5.
Ground 4 has the ground for the flasher and the front AUX connector ( that also supplies the ground for the heated grips).
Ground 5 has the ground for the headlights and the horn.
That list of grounds looks like a list of your issues so I would suspect all 4 wires. :(
On my '06 Uly I have had all four of these break at some point ( some multiple times) and re-terminated with a little extra wire and a careful re-route to prevent any snagging and that has been good so far. I have planned to re-wire this but haven't done that yet.
When I was using the '06 to commute the bars would be put into the steering lock position every 40 miles so in 60,000 miles there was a lot of stress put on the front loom.
On my '09 XT I have yet to have any issues but it appears to be the same set-up as the '06 so it is probably only a question of time. In contrast to the '06 most of the '09 miles have been doing longer trips so way less stress on the front loom.
When you inspect these look really carefully - it is quite common to have the wire break internally and leave the insulation intact giving you a false sense of security on a casual inspection. Tug gently on each wire just back from the ground point and any wires with an internal break will be slightly 'stretchy'.
I don't see any need to use RTV - I have not had any corrosion issues. I used normal automotive style crimp terminals and added and inch and a half or so of wire - I soldered those joins and covered with heat-shrink. I can't remember how many strands are in the existing ground wires but I just used some scrap wire that was the same (don't go less as that will be less capable of handling the flexing).