They worked pretty okay. Mana Vampire in particular. They get resisted very easily though. When mage duelz became a big "thing" around the real UOR-era occasionally I would throw a "hail mary" and try a Mana Vampire. It was resisted 85% of the time even then, but when it worked, it meant definite success in combat at a time when people couldn't run away as fast and (let's be honest) most pvp was based on "throw everything you have at them" strategy. Keep in mind this was also a time when almost nobody had GM resist. It may be totally impossible now with GM resist being so easy. Mana drain was used to by at least 1 guild I know that would take a group out and tame White Wyrms. Everyone would drain it, making it less frisky with the spells. It doesn't really have much utility here it would seem though. I made up the 85% stat above, but my point is "extremely rare". People used to get me with it all the time though since I didn't have resist on my thief at all.