I like this option.
But lately I am being swayed by the “share the emblems” strategy.
As Kerridoc has said, there are some natural break points.
X*+1 for strong talents or talents that match special skills.
Attack X*+2 for color stacking heroes.
X*+15 for 5/5 talents
X*+19 for non Paladins
X*+20 for good Paladin heroes like 3*+20 Tyrum and 4*+20 Guardian Falcon.
None of these heroes can do Sorcerer class quests. Which gets more sorcerer emblems.
Except for self heal / minions / random boy there are no other Sorcerer healers. And 42% Heal is powerful.
Delay is especially useful against reflect damage, and other defense buffs, so it goes well with Fog of the fallen ( looking at you rare tiger titan ).
I will probably take Sabina to at least Attack+HP 4*+15 for color stacking and Delay 5/5.
But yeah, there are a lot of good 4* purple heroes to level for challenge events, class quests and rumored challenge raids.