Because he was and in my opinion is the best damn healer in the game. Quick CD on his heal, a good amount too, does a decent amount of damage (not as much as luminara but he is a healing battery and not a damage dealer) and he was cheap to gear up too (490 purple and 3 raid pieces)
Luminara yes has 45% of her maximum health healing (around 706 more basic healing plus another 2901 the next 2 turns but the buff can be removed) and a 4 turn CD with no chance to lower the CD.
Barriss well unless you have other characters with a lot of health you can borrow from I do not find her useful (she was alright vs. Sidious and the healing immunity but that time is over)
So I do believe he was worth the mats but I do agree his Attack as Defense could use a little boost of some kind
And to show I am not lying about having him at gear 10 here he is (he isn't finished yet and I changed the mods a bit around which hasn't been updated yet)
https://swgoh.gg/u/linkytriforce/collection/jedi-consular/He is good for GW and even some rancor raids but i'd never use him in arena