After tinkering with this new (more like overhauled) support gem I found some interesting mechanics and benefits to use it. First a detailed explanation mechanics:
TL;DR at the bottom
The Inspiration Support consists of two parts:
The first one grants you an inspiration charge when you spend mana with a skill supported by it, up to 5 charges. This doesn't matter what type of skill you use - be it an attack, spell cast, totems etc.
This creates a mana counter to
all skills linked to an Inspiration support, up to 800 at gem level 20.
Once you use a skill that will increment the mana counter above the threshold, the mana counter is reset to 0 and the charges are removed.
What this means is lower mana costs result in higher avarage damage. e.g if it takes 100 mana to cast a skill, the first 5 casts will avarage at 50% of the gem's potential and then the next 3 casts will be at 100% potential, while a 1 mana cost skill will result 795 casts at maximum efficiency after the first 5 casts.
The gem also has a 115% mana multiplier (relatively low) and 25-34% reduced mana cost of skills, which is additive with other sources of reduced mana costs.
The second part grants more elemental damage and increased critical strike chance per inspiration charge, and this is where it gets interesting -
inspiration charges are shared between all skills. It doesn't matter which skill created the charges, each skill linked to this support will benefit from the charges
even if it doesn't use mana.
So why this is interesting?
Two builds that immidietly came to my mind:
CoC: Attacks usually cost much less than spells, especially Cyclone, resulting in higher efficiency. In addition the gem will support both the attack and spell(s), and grant the attack skill a much needed critical strike chance to help proc spell casts.
Autobombers: Since heralds only scale off of elemental damage (and not spell damage) and also crit, this gem fits perfectly in this setup. Using shield charge is very common in these builds and has very low cost which makes maintaing charges easy. (havn't actually played an autobomber before, so correct me if I'm wrong here)
While this gem doesn't have the highest multiplier numbers (40% more at level 20 and 5 charges), it's important to note that the downside of this gem is easly managable (generating and maintaing charges) while other gems come at a steep cost such as crit chance reduction or being unable to inflict elemental ailments. It is also a more
elemental damage multiplier, which is harder to come by.
Overall I think this gem is really good, although unlike it's main purpose I think it mostly benefit skills which already have a low mana cost (channeling etc.) and have some nice synergies with certain builds.
/End Wall of Text.
TL;DR Inspiration Support works well with CoC and Autobomber builds. Inspiration charges are shared between all skills.
