I'm not calling myself an expert, but I'll try to summarize the things I usually do in a voidstar. Note: my gunslinger is only L40 atm, but I can try to set some basic tips for the AC.
Rule 1: Because the Sniper is a ranged class, I tend to put myself way in the back.
Avoiding the zerg and keeping your distance from the objective will put the attackers in a tight spot. Attackers go near the node, where melees will stop them while I support their DPS. Or they come for me, but they'll be too far from the node, stalling for time.
Rule 2: Sniper have many CC tools, don't abuse them
1. Baseline CC tools:
- Debilitate/Dirty Kick: A 4 second hard stun at melee range.
- Flashbang/Flash Grenade: An 8 second AOE mezz, 30m range.
- Pulse Detonator/Cover Pulse: AoE knockback and a 5 second root on all affected targets. First 2 seconds it doesn't break.
- Leg Shot: 5 second root. First 2 seconds it doesn't break on damage.
2. Spec specific CC tools:
- Marksmanship/Sharpshooter: Knockback on Aimed Shot/Ambush.
- Saboteur/Engineering: Slow on single target ability + slow on AoE area ability + 2 second stun when these two are combined
- Lethality/Dirty Fighting: Slow on AoE ability
3. When to use CC:
- Flashbang/Flash Grenade: I usually use this during transition phases, where everyone is trying to get to the screens. I make this decision because not everyone has their CC breaker available and usually they focus on moving forward instead of fighting. This can make some people really fall behind.
- Debilitate/Dirty Kick: I only use this for self defence
- Pulse Detonator/Cover pulse: I use this to peel multiple enemies of myself or a teammate (usually healers). It's also fun to sit in cover on the bridge and knock them off.
- Slows and roots: Leg Shot I use to keep a target in my LOS, just before a Trickshot/Followthrough or Quickdraw/Takedown. It gives me a chance to load up an explosive probe/Sabotage Charge and a Aimed Shot/Ambush. The slows are usually inherent to DPS abilities, so there's no real strategic use.
4. When NOT to use CC:
- When there's a zerg going on at a node, do NOT throw a Flashbang/Flash Grenade because there's too much AoE and it would just fill resolve.
Rule 3: Pick multiple sweetspots and alternate between them
Rule 1 states that you find a place in the back, away from the zerg, in hopes of staying unnoticed for as long as possible. Off course, remaining stationary will work for only so long, so switch place from time to time. I will try and give some sweet spots of my own, based upon the zones that were given by Polymerize.
- Behind the furthest pillar when you exit the spawn area, close to the health pot.
Advantages: You also protect the health pot. If you see an enemy desperately running for the pot, root and destroy and/or take the health pot. Second advantage is that with the big pillar, you can go fairly unnoticed.
Disadvantages: Your line of sight is obstructed by the pillar. Furthermore, if and when you are noticed, enemies can use that pillar to close in on you. Finally, although a minor issue, you will be the last to arrive on the other side of the fence when reacting to an inc. You have no own speed buffs and you are probably furthest away.
- Against the fence in the middle of the zone, close to the gap in the fence (where you go to switch sides).
Advantages: The most obvious advantage is the ability to quickly switch sides. Another advantage is that you're close to an expertise buff. Everytime it reappears you can just take it. This is a good spot to put pressure on the healers/casters that want to stand in the back.
Disadvantage: You are very susceptible for respawns that want to attack you in the back. Luckily, they can't charge/pull you as long as you stay in cover. You therefore always need to check your surroundings. Also, if you are sitting too far, you can't reliably stop a cap.
- Close to the boxes just on the side of the node next to the respawn area.
Advantage: You are probably just outside of the zergfest for the door, but you are still close enough to provide extra defenses with your scrambling field/Ballistic Shield for your teammates.
Disadvantage: You are just as easily not outside of the zergfest. Move if that's the case.
Sweet spot No No:
Don't sit right in front of the door. You are now in melee zerg zone.
Don't go and climb that fancy plane, thinking you're high and dry. You will only be able to hit respawns at a certain point. It's utterly useless.
Don't sit on the ramp just outside of the spawn area. Seriously, you have no view whatsoever on the nodes.
- Just when you enter the room with the bridge, go to the opposide side of where the consoles are and stay as close to the door walls as possible, while keeping a 25-30m distance of the console.
Advantages: People tend to tunnel vision the console when they enter. You can stall caps from there. When melee want to attack you, they are further from the console.
Disadvantages: The moment people notice you, you are a sitting duck. Healers tend to stay in the center stage between the two consoles to easily heal both sides. That possibly means you will get no healing.
- Center stage near the expertise buff.
Advantages: You can easily control both sides of the consoles, delaying opening the bridge. Furthermore, you can use the expertise buff every time it reappears. You are also a good lure so friendly PT's/Assassins on the other side can pull them off, if they are clever enough to see it. Engineering/Saboteur specs can very easily delay console caps with Orbital Strike/XS Freighter Flyby on one side and Plasma Probe/Incendiary Grenade on the other.
Disadvantage: Obvious disadvantage is that enemy respawns land on top of you. You'll also have to move out of cover a lot of times to avoid LOS-capping on both sides.
Sweet Spot No No:
Again, I will never sit right next to a console.
- The pillars closest to your spawn area (next to the ramp with the expertise buff).
Advantage: If you place yourself properly, enemies coming from the bridge won't easily see you. This is especially true if there are some melee teammates waiting in front of the node. You also have an easy transition between the two sides AND you can halt enemies coming from the other side.
Disadvantage: When entrench is not up, there are some fairly easy combos to eliminate you easily, most notably a juggernauts/Guardians Force Push.
- Next to the health pot.
Advantages: Again, I am now in control of who will take the health pot. The pillars are now closer to the bridge, so LOS'ing you will be more difficult.
Disadvantage: People will see you this time. You are slow to reach the other side. Smart enemies coming from the bridge will be able to LOS you for as long as possible using the pillars that are now close to the bridge.
Sweet Spot No No:
- Never right in front of a door.
- Next to the ramp is OK, on the ramp not OK.
I need to test whether or not it's possible to sit on the edge of the ramp just below the spawn area and check the LOS issues from here.
A lot of people tend to stop running and go for the first console, but some of them go for the last. I base my location on what is needed, but I'll almost be close to the second console. The distance to the first console is still enough for my range and I can rapidly switch to the last console in case of cap. it also gives me a first free shot on people respawning, rooting them there for example when they fall to little ledger below.
Here, I like to sit just on the corner right when we leave the spawn area. It gives the possibility to quickly switch between sides without even moving that much.
I actually don't have that much information regarding this zone because we usually don't get there.
I will have to write this some other time, but there's one thing I'm thinking of, based on your rule:
As a ranged DPS, you can have good view on the door. Keep your burst for the right time.
AGAIN, I'm no expert. I don't even have the class on 50 yet. Just my thoughts from playing in low level pvp. Maps don't change when you reach 50 :-)