Gunbreaker, like PLD, is less chaotic and more methodical. Unlike paladin, however, it is more actively damage oriented. It plays like a melee DPS with many defensive options. If you are ever missing a skill, go do your class quests to get it.
GNB starts at level 60, but I will keep the level tiers since they apply to synching down in content.
For GNB, by level 15 you will have:
lv 1 - Keen Edge - First combo strike
lv 2 - No Mercy - boost personal damage for the duration
lv 4 - Brutal shell - Secopnd combo strike, also restores HP and adds a small barrier to the player.
lv 6 - Camoflauge - Increases parry rate/lowers damage received for the duration.
lv 8 - Rampart - Personal defense buff, 20%
lv 10 - Royal Guard - tank stance. Set it to gain aggro, remove/ignore it only when you aren't tanking.
lv 10 - Demon Slice - first AOE strike.
lv 12 - Low Blow - Single target stun (ability, works on cooldown, does not activate GCD)
lv 15 - Lightning Shot - Ranged pulling attack. Generate extra aggro even without stance on, highest aggro skill by damage.
lv 15 - Provoke - Makes you the top aggro target in the team. Mostly used when there is more than one tank and you need to swap aggro, but also used to pick up aggro if the tank dies, or after you die and are revived during a boss fight. Limited use as a longer ranged pull to start a fight.
At level 15 you can start tanking dungeons, specifically sastasha. Keep up Royal Guard and use Demon Slice on groups of 3 or more. Only use your single target combo skills (Keen Edge into Brutal Shell) when there are 2 or fewer enemies, or at bosses. Use these levels to get a good feel for your AOE range on Demon Slice. The ranged pull can be used to start fights, but once you know how to hit everything with your AOE as they rush to meet your group, you won't need it much. It mostly is for dragging in things that escape or go after another teammate. This tier has more defense on GNB than WAR or DRK.
By level 30 you will have:
lv 18 - Interject - used to silence a single target (use when there is a flashing cast guage on a target)
lv 18 - Danger Zone - Single Target Ability, weavable.
lv 22 - Reprisal - Lowers enemy damage in an area, defensive ability. Can be used on bosses, but also useful against groups between bosses.
lv 26 - Solid Barrel - third combo strike.
lv 30 - Burst Strike - Uses one cartridge to deal decent damage to a single target.
By this tier, you can now gain a cartridge for every 3rd combo hit, which you can burn for a burst strike. Be sure to time No Mercy so that you can get off as many burst strikes as possible during the buff, as well as a use of Danger Zone.
By level 40 you will have:
32 - Arm's Length - a personal buff that inflicts anything that strikes you physically with slow. Using it alongside rampart can /dramatically/ reduce the damage you take from a large pack of monsters. (does not work against enemies that only cast spells.
38 - Nebula - Reduces damage taken by 30%, your strongest defensive cooldown outside invuln.
40 - Demon Slaughter - Second AOE strike, adds a cartridge upon successful combo hit.
Only real difference here is you can now use burst strike on single targets during a pull after every/other Demon Slaughter combo.
By 50 you have:
lv 45 - Aurora - Targetable regeneration. Can be used to heal others but is mostly used to keep yourself going.
lv 48 - Shirk - Transfers a portion of your aggro to another teammate. Useful for tank swaps and not much else.
lv 50 - Superbolide - Reduces your HP to 1 but prevents almost everything from lowering it beyond that. This invuln lasts for 8 seconds and makes healers mess their pants o3ob
Gunbreakers cannot hit level 50 except by synching down, so unlike the others, you better already be geared at least this well and have some idea how to tank. Otherwise you are in for a rough ride.
By level 60 you will have:
lv 54 - Sonic Break - Single target heavy DOT. Be sure to use while under No Mercy for maximum effect.
lv 56 - Rough Divide - Singe target rushing attack. Can be used for movement or saved for No Mercy to maximize damage.
lv 60 - Gnashing Fang/Savage Claw/Wicked Talon - Single target heavy damage combo. Requires one cartridge to start, but also has a cooldown.
This is the entry level tier for GNB. 52 also adds the barrier effect to brutal shell, so before then it just heals. Your main focus should be on getting your highest damage skills off during No Mercy (Danger Zone, Gnashing Combo, Sonic break, and Burst Strike) and otherwise keeping up combos and defensives.
By level 70 you will have:
lv 62 - Bow Shock - AOE DOT ability, strikes all surrounding enemies and keeps them draining HP.
lv 64 - Heart of Light - AoE Defensive, best used to shield your party from an arena wide boss attack.
lv 68 - Heart of Stone - Tankbuster defensive. Low cooldown personal defense skill.
lv 70 - Continuation - Adds a second strike to certain skills as a weavable ability.
This is where Gunbreaker starts to shine. You now also want to hit Bow Shock during no mercy, I usually combo it with Sonic Breack just to make sure they stay on the same cooldown. Your other skills are defensives, but Continuation adds a secondary lower damage strike to each hit of the Gnashing Fang Combo. This design was based around the trigger strike mechanic in ff8, and makes your damage combo significantly more impressive.
By level 80 you will have:
lv 72 - Fated Circle - Stronger AOE strike, uses one cartridge. This means it can be used after Demon's Slaughter in most instances to create a 3 strike AOE combo
lv 76 - Bloodfest - Fills both your cartridges. If used while one is full, you only gain one cartridge so use it when you are empty.
lv 80 - Blasting Zone - Upgrades and Replaces Danger Zone.
Plays the same as 70 except you now have an AOE use for catridges, get a couple extra free carts every so often, and blasting zone is cooler and more damaging.
At level 90 you will have:
lv 82 - Heart of Corundum - upgrades and replaces Heart of stone to add a heal after it expires or after your HP dips below 50%.
lv 86 - Hypervelocity - Adds a continuation use after every Burst Strike.
lv 90 - Double Down - A high damage AOE. It takes two cartridges to execute, so make sure you have 2 ready each time you use No Mercy to maximize the damage of both your buff and this skill.
84 adds a second stack to aurora and 88 lets you stack 3 cartridges maximum. Your biggest change here is making sure you got 2 cartridges ready every minute for a No Mercy Double Down, and start using hypervelocity after every burst strike.
Level 100 (7.0) early update:
All 30% tank mits have turned into 40% tank mits with healing/shields to make them one man army mitigations for large pulls.
Rough Divide is now Trajectory, no damage.
Fated Circle gains the continuation action Fated Brand, an additional aoe strike.
Double Down will now prime you for a 3 strike massive aoe combo (Reign of Beasts - Noble Blood - Lion Heart) (and just in time for the Mufasa movie o3ob)
With the Double Down changes, you likely want to hit your DoTs right after No mercy, then doubledown+beast combo, then your Gnashing Fang combo for your buff phase.
As before, the bars are only included as a general idea of what pairs well with my setup. Find your own best setup to maximize damage o3ob
