In highlander, I've only ever played soldier in low-mid gold, and personally I hate all hl that isn't 5cp or koth so take this with a grain of salt. I dunno if this is a joke thread or not, but if you're serious (and if anyone finds this via google or whatever)...
Super Basics
Typically, flank plays E and combo plays A-D. Engie builds guns far back and wrangles a lot. Pyro rotates a lot. Spy needs to gather lots of info.
Basics of defense
pre-a cap
You start the round with your combo holding A and your flank/ pyro/ engie playing B. Your combo's goal at A is to force the pop out of the attackers and then to retreat to B through spawn. A is typically given for free (much like GPit A) except in rare ironman defenses. When they pop, you get out through spawn and fall back to B.
post-a cap
Your combo should be out at B with full uber advantage and a level 3. If you forced a pop at A, you're golden to hold B for free for a while, just be ready for sacks. Your combo should be playing outside at B passively, forcing them to come to you. When they do come, fall out through B-E and avoid popping at all costs. Push back in after their uber and pop.
While combo is holding B, it's flanks job to watch last. It's easiest to do this with a scout, soldier, and pyro standing in the B-E connector. You just spam whatever gets on the point, make sure their engie doesn't build a tele anywhere inside the E/ lobby area, and make sure your medic doesn't die to spies or other stupid flank stuff. The pyro's job is to play both combo and flank depending on the situation. Spycheck around, but make sure the enemy soldier doesn't get free spam on your soldier/ scout.
When loosing B, it's important to have your engie have enough time to set up a level 2 or 3 on C.
post-b cap
Your combo should be playing in the C to D connector (but not too far back because those connectors are nightmares), and your flank should be playing in the lobby by E. At this point, it becomes normal for combos to try and push E. Be ready to rotate when that happens.
C is pretty long and hard to enter from anywhere other than B-C connector, so really it's just a matter of spamming those corridors and denying entry from behind the rocks.
If the attackers have a pyro on flank (by A-E), it may be good to send your pyro over there depending on how good the enemy spy is (you can usually figure that out by this point in the round).
Once again, it's important to get out with uber if possible. But this is a point that is very easy to hold with uber, so don't just run away with it.
post-c cap
D is often hard to contest, so unless the enemy team is bad I'd recommend sacking some player at D for their medic and having your engie/ combo set up at E.
post-d cap
E is (obviously) the deciding factor in steel. E holds can last 30 seconds or 15 minutes, and they make or break your rounds. What's important here is having your pyro with your engie during the actual push faze, a sniper watching the sniper hut, and your flank/ combo rotating to fit to the needs of the hold.
A few things that are also good: soldier can roam a lot here. Pyro can hide and nullify ubers with airblast into the death pit. Spy can relay information (that's often more important than picks during E holds). Scout should be watching the places the spy can't to call that info out. Really, it's an easy point to hold if everyone is on the same page, and everyone is thinking.
Basics of Offense
round start
Have your (working on this part, check back in a second)