Are the numbers too high?

[Rydin]

attack materias are OP

30 Att is the highest you can get...
the Base for Att is like 500
That means the best Att materia increases your "Att stat" (remember, it increases the stat. Not to be confused with your damage) by 6 percent
The damage you deal isn't derived just from your Attack Stat
In fact weapon "Damage Output" is by far the most important stat for figuring your damage.
So a materia that adds a 6 percent increase to the stat that isn't even the most important stat when calculating damage dealt...
A Tier IV Heaven's Fist is actually pretty paltry overall