Most of the oddity probably comes down to rounding.
Your values look about right coming out of the formula EQEmu has for pre-SoF clients:
Code:
if((( Wis - 199 ) / 2) > 0)
MindLesserFactor = ( Wis - 199 ) / 2;
else
MindLesserFactor = 0;
MindFactor = Wis - MindLesserFactor;
if(Wis > 100)
max_m = (((5 * (MindFactor + 20)) / 2) * 3 * GetLevel() / 40);
else
max_m = (((5 * (MindFactor + 200)) / 2) * 3 * GetLevel() / 100);
All the variables in there are integers, meaning decimals are truncated after each division operation. With that in mind, it matches up pretty well.
Comes down to about 10 (flip flops between 9 and 11?) mana per wis pre-200 at 60. After 200, it's not that you get half mana per wis so much as that every second point of wis (the odds) doesn't count. Which would explain how +3 wis can look like very little.
All that's assuming the devs haven't mucked with the clientside calculations, though.