I actually normally use rockets to get away when I know it's too risky to gamble for a kill. After I land just keep running or RJ away again. Gunboats ftw.
I don't see how Thundermountain is Soldier playground though. If anything, it's Hightower that's Soldier playground. So much vertical space. All 3 floors of the tower have big health packs which is
awesome. Those 3 will keep you alive without a Medic, giving roamers a lot of advantage.
The annoying thing is if there's a good gunslinger Engie on the other team. A mini sentry on the top floor is pretty destructive.