There's also to consider the fact some are actually translated in multiple different ways but are the same thing in the chinese original game.

Fixed, given and certain chance are actually the same effect.

High and very high too.

The categories are actually 4:

1) Fixed/given/certain chance: the effect is not affected by secondary stats. It's simply a random roll.

2) a chance: there's a basic probability modified by secondary stats

3) Small chance: like 2 but the basic probability is lower than in case 2.

4) high/very high chance: like 2 but the basic probability is higher than case 2.

Try to face a ninja that owns 10k more combo/control/critical than you and you'll see how random is...