By the time you reach cure V, the bonus you get from wearing +mnd isn't worth it. Adding 10-15hp cured onto an already 700+ cure by wearing +30 mnd isn't worth the trouble. Plus it is already hard to fit an entire cure V in because someone else in the party typically starts throwing out cures at that point too because they don't trust you(eg: pld, rdm, brd, blm).
However, mnd is still useful for a whm, just not really for cures. 10-40 I was commonly only enfeebler (and even 40+ when with brds), so this is when having some +mnd gear pays off. However, you will want 2 sets of gear. One with all +mnd and the other with all +mp. Switch to +mnd while enfeebling with /equip macros, switch back to mp for the rest of the time. Even if you aren't getting resisted it is good to stack on more +mnd. How often paralyze kicks in to block attacks is strongly related to your mnd vs mob's mnd for example. Thus, the more mnd the better even if you aren't getting resists, plus less chance of getting partial resists that cause your spell to wear off earlier.
A little +mnd at the lower lvls is useful to cap a new cure spell after you gain it, but once your healing catchs up and you get a couple lvls past that new cure you won't have trouble with it being uncapped. Plus by the time you can usually start using the new cure it is capped (eg: You don't use cure 3 as your main spell right when you get it, usually wait 5+ lvls).
