Here is the rotation of Red Guardian, by Zipfile:

* Use different (ST/AoE) Weapons accordingly, for boss fights use the ST Weapon, and for heavy AoE fights (such as trash fights), use the AoE Weapon.

Rotation 1 – Boss/PVE, not expected to take damage:

-> Brutal Charge -> Hammer Down -> Stamp -> Sting -> Brutal Assault -> Ignore the Pain (doubletap for instant cut if possible) -> Sweeping Cut -> Sting

* If parry response is gained from the first Sting, don’t use Sting after Sweeping Cut, use Retaliation instead and -> Whirling

Then Sting again -> Thrust -> To The King -> Stamp -> Sting
(if parry response gained from either last two used Stings, use War-chant, then Retaliation again)
Overwhelm -> Sting -> To The King.

This is the basic opener, after which you repeat Brutal Assault (animation cut with ITP or Stamp) and Sweeping Cut (ITP or Stamp again if possible).
Key notes now is that the Guardian rotation isn’t static at all and its very adaptive. You have to balance out multiple things during it:

1. Make sure all 4 bleeds are up and prioritize getting the ones that aren’t.
2. Spam Sting constantly, whenever its off-cooldown. Plan which skill you’ll use next while looking at Sting. Longer skills are sometimes better not to be cut because you can save the cuts for Overwhelm/To The King)
3. Unmentioned skills (Stagger, Vexing Blow, Forced Opening) are your filler skills. Use those when you have all 4 bleeds up to delay the rotation a bit.
4. ALWAYS INTERWEAVE STING BETWEEN SKILLS, it’s your most crucial skill in the entire rotation and one of the highest damage dealers.

Rotation 2 – Landscape/PVE, expected to take damage:

Brutal Charge -> use War-chant at the enemy pack out of combat (this gives you the crit on all enemies hit without consuming the Brutal Charge buff, giving you second used skill the 100% crit buff too) – gather mobs – Sweeping Cut – (if you didn’t get a parry response, Forced Opening) – Whirling Retaliation – cut with Stamp/ITP – War-chant – (mobs should get back up by now and you will most likely get a parry response from being hit) Whirling Retaliation – Thrust – To The King.

This is the basic AOE opener, just spam AOE skills and Sting, if you’re getting low on health, use cooldowns as needed (Catch a Breath should be the first one, Thrill of Danger, then Pledge, then Warriors Heart, by the time this is all out and if you spammed War chant, you’ll have Catch a Breath back).