This honestly seems like a really cool idea, especially considering that hunters have a somewhat similar feature with fire arrows; Fire arrows have a small chance to inflict embers on surrounding mobs. It would be nice to have more options between charms for fire mages, because while 2 seems to be enough for me, water mages can switch between 4 different charms. On the other hand, the Charm of Wandering Flame exists if you're interested in increasing the amount of area your AoE can cover for multiple mobs, like those bothersome spiderlings.
That being said, if the AoE regen from ignite weren't nerfed somehow, you'd be able to regen ~50% of your mana from a large group of mobs, and even more if you have a high magic power, which would result in a really OP charm. For example, my spirit bottles and arcane magic allow me to have 850 magic, and so I can already regen 15-20% of my mana on something like an Earth 4 mob. This charm would either have to be rather difficult to obtain, or only provide a pretty small fraction of the mana you'd receive from ignite, because a mage with a DPS higher than 1.4k could easily exploit it. I'd be really interested in seeing how this charm plays out in PvP though, because it would really help with the drain of mana that comes with battling a group of people with high HP, like warriors.
