On hold! At the moment I'm scratching my head finding a way to balance her without either making the passive worthless or nerfing her passive-less damage into the ground entirely. Will come back to this at a later date!
Background to come!
Another, kind-of parallel approach to power growth alongside Kegan Vulcana, the Inferno. Unlike the aforementioned example however, where you are focused on being as active as possible, Shadowcat relies more on the summoner's tactical decisions in any given situation. Her base damage is rather weak, but she does scale rather well with AP bonuses. Her base damage can be greatly multiplied by repeatedly activating the same ability within a short duration, at the heavy cost of increased cooldowns which cannot be mitigated by any CDR. If "weaving" her spells by casting each one in turn as needed, her damage and support will stay low compared to others, but she doesn't have to worry about being restricted to a resource or cooldowns.
To help with this, her ult is a moderate length steroid which effectively gives her a flat damage/healing boost to everything she does, with the cost that it can be killed effectively eliminating the "buff" early. This is the only ability that is affected by CDR from items, and can be very effective in not only increasing her overall support in a team fight situation, but also allowing her a large spike of damage on short notice should she run across someone while alone.