Isarnia is slow and glassy.
OP already has better options for blue 5* 4.80
and 4*+18 ( looking at you Miki and Kiril ).
Edit:
Double checking current 5* blue.
Actually COSTUME Isarnia would be a beast for normal/ matching/ tile damage in a blue stack with Miki.
See also
([Curiosity] What level Isarnia equal to Grimm's 4* 4.70 base stats ? Update Vivica & Rigard)