I've considered it but never tried it. The returns when the target dies are all % based which is pretty dang strong. Plus in the next update one of the crafted sets will increase soul trap damage..,
I use soul trap constantly. First off, go with the other morph. 3 soul gems is way better than 1. Secondly, in PVP it will help slightly (tags 3 opponents, damage over time) but only slightly. I only equip it in Cyrodiil if I'm running a cave. It's much more of a PVE ability.
It's Godly in PvP if you have a group of any size or solo burst 10% of all resources, plus pets and engine guardians count. Need stamina or magic two wolves near by 20% every thing right there. Now it's never on my main bar cause poor damage but off its their as a magic Argonian Nightblade.
Chaos Shadow-Scale: Shadow Archer
Chaos Death-Scale: Shadow Knight
Tanks-With-Sap-Essence: Dark Mage
Dark Brotherhood Listener: Blade of Argonia
Chaos Dragon-Scale: Draconic Shield Master
Chaos Light-Scale: Marsh Paladin
Chaos Lightning-Scale: Daedric Master
Hurricane Chaos: Storm Archer
Bask-In-My-Light: Warrior of The Light
Forged-In-Dragon-Fire: Pyro Mage
Guardian of The Hist: Light Mender
Chaos of Black Marsh: Master of The Burning Sword
Star of Chaos: Frost Blade Champion
Chaos-Lightning-Tower: Lightning Shield Master
For the King of Argonia
May Sithis hold back his Void