Wizards have a decent advantage over other classes in iRO/kRO and thus have the lower weight capacity, as GTB is extremely rare and only another magic class (professor) can completely nullify what a wizard can do in a almost non-GTB environment. You honestly can't compare the survivability of a wizard to that of a priest just because of safety wall. What about long range attacks which bypass Safety Wall? Wizards don't have the luxury of being able to use Pneuma to then render an enemies' long range assault useless. Assumptio > Energy Coat, as being hit while having a Coat active means your SP constantly being drained, and as for Ice Wall goes, see previous comment on Long Range skills, as well as GTB rendering anything a Wizard can do useless, besides maybe a meager 5k-20k Stave, if that. Even if we were to allow wizards to carry upwards of 300 Yggdrasil Berries, what are they supposed to do in terms of offensive? They can't use coma (Lord of Death Card Coma Chance is a joke), and your enemy will have GTB on anyways, or do any real damage with melee as they have no Mastery skills, and no I don't play wizard.
On what you say about Priests.. VapoRub obviously only discussed Int-Based builds because if you choose to go battle (read: STR) builds, you'll have the capacity of carrying more berries naturally. Priests have Pneuma, Safety Wall, Assumptio, the capacity of being able to switch and actually efficiently use STR builds while threatening with coma, their chances of surviving is much better than a wizards, and can actually do something in return if they wish to. The most a Priest needs in this server is an Elite Mace so they can take advantage of their Mace Mastery skill.
On the Ninja comment, have you tried killing a Ninja with fcp on your champion? What are you exactly supposed to do? It's true that you can sight them to prevent them from hopping around and then push them against a wall, but even then they can avoid all your damage by spamming Cicada as they try to walk away from you again. I don't see a good ninja going down so easily, or having to spam Yggdrasil Berries unless they use Final Strike, and a good Final Strike build requires STR anyways.