Unless you are soloing, any race based regen becomes almost useless by the time you're in your 20s. And I don't see many SK's soloing on this server. Not saying they can't, but it can be tedious and with the exp penalty being what it is for a troll SK. I can't imagine anyone preferring to fear kite solo instead of being in a 6 man exp group. (edit, besides Marl
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This is also the reason why I never put much value in the Rubicite BP. It's fun for a low level twink but quickly becomes inferior to something that provides HP and stamina.
The only case where race based regen NEVER looses its usefulness is if you are playing a necro or shaman. Those classes can solo effectively throughout the entire game and are HP dependent for maintaining good mana flow.
(Complete side note: I remember the first time I saw a shadowknight soloing trash mobs in the plane of disease. I know it's not rocket science or anything but back in the day I was immensely impressed. At that time I would have needed mad AA points to be able to solo anything in PoP for exp in my 50's-60's.)