The real problem with Inpetitude+SS was danced around a bit, but not really hit on.
The "meta" for hero builds these days includes 2+ Mesmers. Sometimes Ineptitude is one such Mesmer.
The problem is, even with two Mesmers, you're almost ALWAYS going to have multiple interrupts from Domination and Illusion, and given that the AI isn't great at target switching (i.e. they unload all skills on target A, then move on), your Necro's SS will likely be useless due to the variety of said Mesmer interrupts.
You could of course take Mesmers without interrupts, but then you're ignoring the best part of Mesmer Heroes and that's their godly ability to catch almost any skill in an interrupt. And for the AI, there's serious lacking options in the Mesmer skills anyways, try an Echo Chain E-Surge lol.
I switch between two different melee (Dervish and Sin) and two caster (Mesmer and Rit) characters when I play, and no matter what build I take, called targets are usually spiked down within 5 seconds or less, which given the attack speed and casting speed of mobs in HM meaning SS will at most trigger 3 or 4 times, then factor in the amount of movement HM melee does on kiting heroes, and SS just loses its lustre.
SS isn't bad for a human in specific conditions as mentioned, but I wouldn't stick it on a Hero in just about any situation.