Is using a Bow and Siphon usesless?

Elyna

Compared to the assassination class, I kill mobs much faster. I rarely run out of HP so the Siphon ability doesnt really seem to make a difference. Secondly, the morph on killers blade to heal you is much more reliable and keeps you in the fight longer.

Am I doing something wrong or is bow+siphon a lost cause?

cbbouletb16_ESO

Assassination tree won't beat a boss.
Stealth spam with siphon and bow will.