Vaal Immortal Call

Vaal Skills should not be built around. They are skills that should support your main build in a way that it can compensate for the lacks your build has otherwise.

In this case, Vaal Immortal call does EXACTLY what its supposed to do. Its not a skill that every build has to use, but just a build that relies on Self-casting immortal call. Imo.
VIC benefits from literally everything that IC benefits from, except for that it saves you from ele dmg too.

So lets determine what IC builds do:

Immortal call builds are mostly Melee, Physical, and use Immortal call to compensate for their vunerability against high phys melee threats, like brutus and follow-ups and Phys Reflect. Immortal Call builds Can use Items like The abyssus without having to fear the drawback and can thus get a good increase of Dps due to that. They can easily get immortal call to run for 20+ Seconds and to my calculations can even go up to 30-35 seconds for high end builds.

Regarding this, Melee builds can be very fragile against bosses that do huge melee Elemental damage. Bosses like Dominus' first form, Piety, and Atziri are also not the most comfortable bosses to fight. If you manage to pull of enough dps though, 30+ Seconds of immortality should make these situations easy to cope with. Even 10-20 seconds for non-end builds is fine enough for the immortal builds to not have to fear Elemental and Chaos damage. Of course, as a IC builds, Unwavering Stance is a necessity, but you arent taking much of a downside from it anyways.

For Reference, The best usage is picking up all 4 gainable endurance charges from tree and bandit, plus koams sign x2, preferably a corrupted belt and 6 15% duration nodes from the tree. (you can even pick up the three 10% nodes too, but for the efficiency, thats not worth it). Then, you link:

Vaal IC (lvl 20/23% pref) - Enhance (lvl 4 pref) - Increased Duration (lvl 20/23% pref)
(which leaves you with a slot to equip normal IC too)
In either a +1 to gems, or in Atziri's Disfavour.

Assuming the +1 to gems, you get:

0.25 + 10* (0.78 + 0.32(from enhance)) = 11.25 Base Duration
11.25 * (1 + 0.765 (from inc duration) + 0.9/1.2 (from tree) ) = 29.98/33.36

Assuming Atziri's Disfavour:

0.25 + 10* (0.77 + 0.40) = 11.95 Base duration
11.95 * (1 + 0.775 + 0.9/1.2) = 31.97/35.55

With Empower lvl 4 corrupted too:

0.25 + 10* (0.82 + 0.40) = 12.45 Base Duration
12.45 + ... = 33.30/37.04

You can understand that 20 seconds shouldnt be hard to reach right?

96 Souls is a huge price to pay. But ey, the effect supports it right? Skills like Vaal Spark have the same amount of impact and for those there is never a complaint about the soul demand.

More importantly, instead of having to take up a whole item worth of links to support the gem, its easily linkable in the same item as immortal call. There is no reason not to slot it in if you are running IC already right?

The way i see it, is that if the soul counts is lowered, the duration has to be lowered too, but i dont agree upon that. Its a very unique effect that can easily get unbalanced when altering it to such a way.