Bonjour,
Déjà désoler si y a une doublon.
Normalement ont était pouvoir censé les raid de légion hors ont ne peux pas je faisait plus de dégâts au mobs quand j’était 50 
J’aurais bien aimer pouvoir enfin soloter mes run tmog/mounts. Hors pour l’instant c’est impossible !
Un hotfix est bientôt prévu ? 
Bien Cordialement Syltia.
J’ai trouvé ça sur wowhead:
Citation While investigating the difficulty of doing legacy content at level 60 in beta, we discovered that, currently, it is way harder to solo Legion content at 60 than it is at 50.
The reasoning behind this seems to be some hidden scaling aura at work for level 50s, increasing the damage for all spells cast. This aura doesn’t seem to be present for level 60s, making them deal significantly less damage and take significantly more damage from enemies.
To show this effect, we have two logs of two naked Shadow Priests casting Attaque mentale against the same boss, Mythic Garothi Worldbreaker.
You can see on both logs that Attaque mentale deals about the same damage at 50 and 60. However, the level 50 priest has 156 intellect, while the level 60 has 451 intellect. This means that the level 50 is dealing 3x more damage than they should. Dealing the same damage wouldn’t be an issue normally, but when you take into account that the level 50 can get much more power from Battle for Azeroth’s systems like Azerite Power and Essences, than a level 60 character will be able to at the start of Shadowlands, things scale out of control.
Below are two examples, one of a level 50 and one of a level 60 Shadow Priest against Mythic Garothi Worldbreaker. The level 50 using their Patch 8.3 loadout at item level 130 with Azerite Powers and Essences, and the level 60 character using item level 190 Honor gear.
Source: wow head
Donc apparament, ça marche pas et les devs sont en train de chercher une solution au probleme si j’ai bien compris