You already said you do not have better options. But just for my curiosity, what are the other options?
Glass cannons
Both Grimm and Sabina are glass cannons. They do very good tile/ matching/ physical damage, but are less sturdy than Kiril or Rigard.
Emblems
Overall, the more important number is how many nodes ( see notes ). There are exceptions, but not Grimm and not Sabina.
Grimm
Role
I use Grimm on my Wu Kong cascade squad ( see notes ), so Grimm’s role is to use Ramming Pulverizer. All DEF/ HP helps with this role by keeping him alive.
Defense
Grimm 4* 4.70 ( Attack 716, Defense 531, HP 1132 ) has the same defense stat as Gunnar 3* 3.50. So even if you choose attack nodes, defense nodes on the same branch are insanely helpful.
Sabina
I use Sabina as a healer for Sorcerer quests ( use emblems to get emblems ). All DEF/ HP keeps Sabina alive so she can keep rest of the team alive so I can get those emblems.