Perseus
Gryphonkit, my wife, and I have Perseus since the first time they were available. We both have every blue paladin HotM in the game. merciless RNG is weird
Roster
( say it all together) Leveling Perseus really depends on your roster.
Field Aid
And how much you hate enemy healers / Field Aid ( WR ).
(Can we just get rid of Field Aid already? - #103 by Gryphonknight)
5*+1
Gryphonkit, my wife, loves Perseus at 5*+1 .
5* 3.70
I use my Perseus 5* 3.70 all the time, especially in Field Aid ( War Rule ). Usually in a 3x neutral blue stack. Non dispellable, -100% healing for 4 turns on a fast mana speed special skill will usually take out 2-3 enemy heroes during Field Aid (WR). Was really helpful with Rigard in a corner during old Revenge bar. Arrow Barrage is significantly weaker.
I have a ton of blue in my roster, so unlikely to level Perseus to 5* 4.1+ .
5* 3.70 heroes, and 4* 3.60 heroes, are also cheaper. Good for heroes you use mostly in war or tourneys. Hero XP, and 4* ascension items, are deliberately rare to increase IAP of summons and ascension items.
Magni
2 years, and 3x Isarnia, before I got Magni. I finally had to run 3x Legendary training to get purple 4* Cyprian, blue 5* Magni and purple 5* Sartana ( still missing green 5* Lianna and blue 5* Richard).
So lots of play styles concentrate on what you have in your roster, especially for 5* heroes.
4* ascension items
It also depends on how many ascension items you have.