it's a very overtuned spell. On a proper dd, u can do 80k damage with just that spell alone (counting the synergy too).
and during a parse, even solo, you will see that it has a good spot on the list (tracking with addon).
It's definitely a strong slot for group content, but most people just ignore it, and mostly in pve it's magicka

tooltip on my "tank" that has two sustain sets and without any buffs active
8655 instant, 11539 after 10 sec. Synergy for 19715, summon spider to attack for 10 seconds for 3243 per attack and can poison them for 20184 over 10 seconds.
so 39909 instant counting with synergy and including ending bursting too, we're half way there.
now spiders let's say they attack every 3 seconds, but i think every 2. It's 3x3243 = 9729, with a chance for another 20184.

so total unlucky will be 49638, and with at least one poison proc u add 20184 to a result of 69822.
if spiders attack every 2 seconds i think, just add another 2 instances of 3243, u can do the math.

and this is on a character with 34632 stamina and 3569 weapon damage, unbuffed. You will very easily hit 80k mark with a single cast, counting the synergy being used in a group.

Use it on almost all of my stam DDs, very stronk.

You need some group coordination with a ranged character always ready to trigger the synergy, and for fights to be static enough enemies are standing in almost the same spot for a full 10 seconds. Not easy to achieve on normal dungeons or pugs.

Trash mobs often don't last half that long and bosses ... tend to move around in pugs.

I used the heck out of it for moons. I used it to keep enemies in my Unstable wall longer. Also very nice when mixed with Sellistrix to keep them close to the stun quake.