you twink with consumables when synced below 111-119. a 120 in 20-29 can use bfa battle pots(level 100 req) and shieldtronic shields (level 91req). the buff/absorb amount is scaled down but are better than anything a 20-29 player has available. boa neck and boa trinkets with on use are also able to be used while syncd. the ideal toon to sync on would be a dk since their runeforge weapon enchant is active.
Yes, however in 20s there are so many 20 vets/ftps geared with enchants/set bonuses/pots while premaded(using of course Arcane mages) its definitely one of the most difficult brackets to party sync into.
If you are party sync ing in the world your spells doesnt change because mobs scale to your level up to level 60.
Its not broken. Git gud.