I see very few people actually using that morph. It's not hard at all to find out why the skill is so ignored across the board in necromancers: there's far, far more viable ones. I don't want to get into the discussion about the necromancer design when it was released in the game, since the community is so divided about the whole 'raising a little army' thing.
But the more i play a magicka necromancer myself, the more i grow frustrated on using this ultimate due to how cool, expensive (320 ultimate) and poorly performing it is even in no-CP. Sure there are more experienced necro players out there who can help me understand this, but why ZOS didn't tune the cost down a long time ago in exchange, for example, the removal of the ally raising thing? I'm totally fine raising one to three blastbones from corpses in a cheaper version focused in generating a lot of corpses fast. That would be interesting to see in experimentation.
Also, i can't really tell which amount of ultimate would be fair to place on a possible new and more specialized version of the skill, but something under the Colossus cost would be fine, since it's a super predictable - not at all sneaky - skill to use during a fight. And let me not get into the fact that the skeletons will chase whoever they want, so forget about calculating a solid burst damage while using it.
Thanks!