Saw a Warrior doing this

[Ashimar]

A Warrior goes to solo a single mob. The steps are taken while in battle.

First, he
1. Hastes himself without the use of CoF/RBB/FBSS
2. Makes himself invulnerable, temporarily to physical attacks,
3. Gives himself the buff, "Feet like a Cat"
4. Roots the mob for up to 45 seconds.
5. DOTT's with Strong Poison.
6. Stands from a far distance while the mob is rooted, he begins
pelting it with arrows.

6. Repeats step 4 then 6 as needed.

How is this possible?