But the reason is very simple and clear, mate. Sorcerer is just the worst of all the Mages and MP regen has nothing to do with it. 🙂
If you want a character with super cool oh so sweet casting speed, you choose Spellsinger. If you are into strong, powerful, bad ass magical attacks, you choose Spellhowler. And if you want balance between casting speed and magical attack, you choose Necromancer. You will not choose Sorcerer, cause necro is just so much cooler – the debuffs, the servitor and transfer pain, vampiric claw for HP regulation … while Sorcerer is actually just a balanced “spellsinger”. So people generally do not choose that class. And it is not an OldSkool thing, it is just a Lineage 2 thing.
That’s why I propose to improve him at least somehow, so that there is interest in it too 🙂