I feel that all the platinum mages have their own niche.

Sasha can protect close allies from some physical attacks on top of have high output (with a AW buff that speeds up her attacking)

Garania is the clear-cut mass-mob-clearer with her ridiculously huge AOE during skill, plus she buffs Mages.

Odette is able to protect EVERYONE from magic attacks and has respectable output herself

Estelle is a black, comparison is automatically unfair

I'd compare Odette to Sasha since they both have skills of a defensive nature. Sasha is anti-physical (but has limited range of protection) while Odette is anti-magical (with unlimited range if I understand correctly). Sasha has better damage to compensate for her defensive skill's limited range. Odette is likely to have comparable cost simply due to the premiums getting CR'd only on rare occasion (expecting people to have min-cost Sasha/Garania is silly; even spending $200 per month on MWA I don't have that)

TLDR: If you have the premium plat mages, Odette still has her niche. If you don't, she fills in nicely.