A few of us did discuss this with you, and here are some points that came up.
1. Some heroes can have similar effects to relics. You’d still be allowing 6-star heroes, etc., so banning relics seems uncalled for. Further, heroes like Hell Keeper or charm/polymorph users can function similarly to relics already. So if you banned a charm relic, then people could still use charm, for instance.
2. Fights like those against Joseph (in the case of this tournament) were likely to end in a one-shot anyway, or something like it.
3. Relics that increase stats are quite similar to just increasing the stats themselves, and that’s allowed.
4. Cross-server Arena does have buffs that increase damage anyway, over time, as well as HP. So in that sense damage increasing relics aren’t that different from the format itself. It’s an artificial context, so it’s possibly exaggerated to say that relics shouldn’t be allowed. This arrangement does benefit the predominant ATK-HP-focussed builds (as does the ability of just about everything to bypass DEF), and these generally arrange their stats such that murder weapon will benefit them anyway. But they don’t just benefit from relics.
5. There’s already enough imbalance to make some players one-shot most people, so banning relics is again not really solving much.
6. Relics as they are play an important role in the set-up of the game, and things would have to adjust to a situation without them. Further, there are still chance elements, etc.
Of course, there are some somewhat reasonable points to be made about relics. They do make the element of luck a more significant one, potentially, and unlike skills with effects (that can easily be balanced, as in many games where moves with such side-effects might deal less damage etc) the relics can typically function with any move. They can also make AoE attacks more important. Further, some combinations of relics, etc., are said to be broken or non-functional. However, players might not be aware of this from the relic’s description etc. Nonetheless, making relics a target – in the suggested way – would seem to be disproportionate given the other factors present.