To answer the original question, I think you can see from the GIF that Zardulu posted that the way the system works, it does not have to be drawn perfectly the same as the example to work. Really it’s more about the overall proportional shape.
Also, the system is 100% consistent. You will take practice to get consistent. But the system is basically just math: same stuff in, always the same stuff out. If you could in theory make the exact same drawing every time you would get the exact same result. Of course you aren’t able to do that without a lot of practice.
I think really my “ideal” progression for a Runemage goes something like this:
Beginner: You know 5-6 basic spells, and you can cast them around 25-50% of the time.
Intermediate: You have 5-6 basic spells down pat to where you can get them to cast 75% of the time. You are beginning to learn another 10-15 spells for various situations but you aren’t as good with them.
Master: You see runes when you close your eyes. You have a cadre of 10 spells you can cast nearly flawlessly via muscle memory. The rest you know and can get 80% of the time.
I think it will take someone a minimum of 5-10 hours to get to Intermediate, and probably 100 hours to get to Master. This is a gameplay style that really is not for everyone. But I can assure you that if you practice the runes and you get to the point where you can cast them consistently (like Zardulu in that GIF), the system will reward you with letting you cast the spell every time.
And, of course, all the runes are changing in the next Alpha test, so I apologize to everyone who has learned the previous versions and now has to re-train their muscle memory that was developing, but this should be the last time they change. The new runes are designed so that basically you should never really accidentally cast the wrong spell (e.g. the old Fireball and Frostbolt runes were way too close together).