Thunderstrike - what am I missing?

[iRFNA]

Aim is so easy to forget. Especially considering the not-so-directly explained mechanic where any precision over 10 counts as "double". So 11 precision is "actually" 12 precision.

So if you take ((listed precision in unit screen + precision modifier from attack/spell) - 5) * 2, you get the real precision being used. The range it can go without deviation is precision/2 - 2, so putting it all together:

range without deviation = (unit precision + weapon/spell precision) - 7
max degree of deviation when over range = (distance to target * 0.625) / (unit precision + weapon/spell precision)

Of course, this is quick math so I may have made a mistake.