[Maxim]

As you level higher it will exponentially become harder to land enfeebling spells if RDM is subbed. Same goes for Ninja, because those spells are based off of the skill level of Ninjutsu which only Ninja gets (so subbing Ninja will cut the skill level in half just like when you sub RDM).

So no, Dispel won't land at higher levels. Even Red Mages with their Enfeebling skill maxed occasionally have a hard time Dispelling spells like Enchantment Magic and Spike spells off of Elementals whose level is a bit higher than the RDM's and stuff.