About elite run at the last map

[rssh0106]

I am a rogue with dps about 190. My level is 21.
Since want quickly end the boss, I keep using "Aim shot' skill to attack.
My critical value could reach 98% when I tap the pet ability(my pet is ribbit), so my damage could reach about 400 for every shot.

While I keep using this skill to kill the boss, two players (also rogue) call me noob?
I don't understand.
Is there anything wrong with this?
Thanks for the explanation.