Issue before the answer
I'd like to point out that having sigils that move/consume/process Anima at different rates means you need some kind of buffer or battery between sigils. If your first sigil moves Anima at a slow rate and your second sigil moves it at a fast rate, then you're second sigil isn't working unless it waits for sufficient Anima to build up to allow the sigil to operate. Since the problem is solved with "buffering sigils" that act like batteries to ensure each sigil gets the Anima at the rate it needs, the differences in rates makes this magic system very complex without a good reason.
Your magic system should work like electricity.
An electric circuit requires a specified voltage and current. If you think of electricity like a river, voltage is the speed (or, unfortunately, "current") of the river and current (see what I mean by "unfortunate?") is the volume of water. Thus, a large, slow-moving river has a small voltage but a large current. A fast but small river has a large voltage with a small current.
Continuing with the water analogy for a moment, your sigils are like water wheels, stones/rocks, waterfalls, land grades, etc., that affect the speed and volume of the river.
Converting back to electricity, your sigils are resistors, capacitors, inductors, transistors, and a host of other electronic components. Each component affects the electricity, depending and using power, defined as the product of voltage and current (P = V • I).
This is useful, because P is the amount of Anima an individual wizard has to work with and how much is needed is a function of the rate of consumption and the volume of consumption.
Thus, a combination of sigils that lifts Marilyn Monroe's skirt are fast with low volume where a combination of sigils that moves a mountain are slow with high volume.1
In terms of your magic system
Now, I want to simplify matters such that an RPG-style rule can be created.
Rate defines how much "time" is required to consume Anima. Rate is a number between 0 and 1 but never 0 (0 < Rate <= 1).
Consumption is the amount of Anima consumed in that much "time." Consumption is a number greater than zero (0 < Consumption).
Yeah... that might be a bit confusing, but check this out, I think you'll like it. Let's define three sigils.
Akdur = influences the spell to create a clockwise spin or twist to the result. Rate=0.2 Consumption=12.
Cheffaw = appropriates the atmosphere around the caster. Rate=0.8 Consumption=5.
Heurist = draws heat from the sun (vs. other sources). Rate=0.1 Consumption=25.
All the rates must even out. That means the largest rate controls the whole spell. We'll assume that one of each sigil is require to create a hot tornado of death!
Longest rate: 0.8. The other rates must fit into this.
0.8 + 8(0.1) + 4(0.2)
And we replace the rates with their associated consumptions:
5 + 8(25) + 4(12) = 253 Anima to get our Hot Votrext of Death!
And there's your power-based limitation
The stronger your wizard (total Anima) the more complex and more powerful the spell that can be cast. Weak wizards need to get creative with the sigils to squeeze the most out of what they can do.
1 I'm not suggesting the same power was needed to lift Marilyn's skirt as to move a mountain — after all, she was known for kinda liking her skirt to be lifted.