I tend to enjoy researching the Math for games like this so here is a cool tip.

When calculating a monster stat with runes, each rune bonus affects the next runes bonus.

That is, the 1st rune will multiply the stat by 100% + bonus%, and then the second rune will multiply that sum by 100% + bonus% and so on and so forth.All runes are stackable when equiped, and it is multiplied from previous value.

For EX, 2 runes of "Life" will give: 1 * 1.20 (1st) * 1.20 (2nd) = 1.44 => increase 44%, not 40%.

Let's take Team Strength Runes at lvl 3 (+10%) and pretend we are using a team with 9 of them.

So the math works more like this.

Total Strength = 1.1(1.1(1.1(1.1(1.1(1.1(1.1(1.1(1.1 x S))))))))

Total Strength = 2.358 x S

For those who are lost, that is 236% Strength bonus by using 9 Team Strength 3 runes.

This is a considerable difference from 190%.

If this was 9x Team Life 6 runes, the bonus would be 516% health. Just thought I might throw this one in for the WOW factor.

TLDR;

1x Team Strength 3 rune = +10%

9x Team Strength 3 runes DOES NOT = +190%

9x Team Strength 3 runes = +236%