If you lose yourself in the exact rotation, follow this priority list.
Use Bladesong skills to keep up the damage buff from . Make sure to delay as little as possible and always use it with 5 Blades. Use Phantasms ( and ) whenever ready. Use to reset your Bladesongs. Use and off-cooldown. You can also weave them in between other attacks, even ones with higher priority.
Auto-attack on Dagger.
Remember that your personal damage skills are faster than phantasms, but that they deal more damage over time, this means that direct damaging skills such as Bladecall and auto-attacks get higher priority if the boss is close to phasing.
for CC, but also remember to not use too much CC on the break bar and space out your big CC cooldowns like Signet of Humility so they don't overlap with other powerful CC skills.
Apart from doing DPS, you'll also have access to a wide range of utilities which can all be used for skips, blocks, and damage mitigation. Make sure to read what they do and don't be afraid to swap to them situationally, especially in T4s.