Bug or what?

[Kel´Thuzad]

I wanted to train the abilities of certain weapons to Rita and Repede, which have less attack power, so when entering combat, Rita and Repede do 1 damage, I changed the difficulties to see if they did normal damage, I even put their strongest weapons , but no, they continue to deal 1 damage. What happened?

[Synavix]

There is a skill called Minimum Damage (or something similar) that makes a character do 1 damage with all attacks. Either you have it toggled on in their skill list or it's on their weapon (all weapons auto-apply any skill effects they have while equipped). There is also one for half damage and quarter damage, and those aren't as noticeable right away, so it's worth checking your skills occasionally to make sure you haven't gotten them toggled on by accident. They're always in the same spot on each characters skill list (near the bottom of the red colored skills), so easy to check.

[Kel´Thuzad]

It was because of that. I completely forgot about it. Thanks friend. Is it useful?

[Synavix]

It can be useful for farming or building combos. I never used the half damage or quarter damage skills (other than to train them), but I used the minimum damage ones to get the combo titles/quests and to farm GRADE at the end. There's a good "afk" GRADE farming strategy that got me about 10k GRADE in 2-3 hours. It's also useful if you want to kill things with Fatal Strikes, since those will still insta-kill even with 1 damage turned on (aside from boss enemies, of course).

But if you're just doing main story stuff then no, I never really used them for that.

[Kel´Thuzad]

So it's just to get trophies, right?