Hope you'll excuse the double-post... the first was long enough and I missed a couple of intervening posts while writing it.
I like the Ring of Beasts too, but generally find that there's something else I'd always rather be using. SEN is nice but not critical to any of the classes you've listed. Now for a Ranger or an Omnigun Gadgeteer, that would definitely be a consideration.
As for the PIE & spellpoints issue, since we're talking items, keep in mind that once you make it to Ferro the Infinity Helm will pretty much take care of mana needs for the Samurai, removing what little relevance PIE may have had previously. That doesn't help the Ninja (and neither do the Robes of Rejuvenation). It does turn out that if you plug in a minimum PIE of 45 along with SPD, DEX, and SEN for the Ninja chart that, not surprisingly, Humans become the best.
But basically once you decide that even for attributes you are not focusing on, you insist on certain minimum values (usually 45-50), Humans automatically become the best race for every single class since they start with 45 in everything and have the highest overall attribute total.
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->Klutz
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