Not all your actions in a action scene are combat.Also for dodging, this charm is vastly superior.
So it is scene long and we do not need a rising difficulty to effect it.
You pop it and enjoy for the rest of the turn by applying it to ALL attacks.
Much better then Multi-arm.
And a bunch of the non-stabby actions will use non-Key Attributes and Abilities.
Also, as @zxzx24 pointed out, 5 dot charm.
Even by the standards of 5 dot charms, its way down on the list of priorities.