Game Mechanics: Int after cap

[Serin]

So, I was doing some gear experimenting yesterday.. and I'm at 210 int and have a mana pool of 2550..

In my main hand I'm using a Tome of Miragul (-5 str -5 dex - 5 sta, -25 cha, wis +6 int + 6 hp +50 mana +50) When I remove the tome, I go down to 2471 mana, which adds up to 29 for 6 int, and 50 from the raw mp.. Now, After this, I tried putting on a harvester instead (+5 str + 5 int -5 dex) and ended up with exactly 2500 mana.. Which means that for me 5 int is = to 29 mana, the same as 6 int is = 29 mana... so.. post soft cap.. is 1 int really not even worth 1 mana?