Some quests in this chain have been completely changed for WOTLK from TBC versions.
1 - As such, some NPCs are not present anymore in WOTLK: M'uru (id 17544) removed, no replacement; Magister Astalor Bloodsworn (id 178420) replaced with id 17718.
2 - https://www.wowhead.com/wotlk/quest=64319/a-study-in-power replaced with https://www.wowhead.com/wotlk/quest=9681/a-study-in-power . Different NPC to turn in at.
3 - https://www.wowhead.com/wotlk/quest=63866/claiming-the-light replaced with https://www.wowhead.com/wotlk/quest=9684/claiming-the-light . Different NPC where you accept (you get it from 17718 in wotlk), different NPCs to use quest item on (instead of M'uru you have Blood Elf Magisters (id 17845)).

7.4.14

Fixed in #4740