Not really, no need at all for Revive Crystals. It just takes luck & attempts (& personally also the aid of an ally deck with 1500000 combat power).
Anyway, the only major reasons to go for the Extreme level are the [SR Guaranteed Special Gacha Ticket] for first time completion of stage 03 & the title "Super Hunter" for first time completion of stage 04. For farming Temple Treasures & other rewards , also I do recommend remaining on stage 04 of the High level.
Oh yeah, wanted to point that out indeed: it is better "giving up" when you notice you can't take it anymore rather than going all out trying to do the best you can.