I was luck and got a slayer who give +50% too.
Rank 262 atm. 177.000 EP with 4,5 out of 12 days gone.
Getting 500K EP will be hard but I hppe new stages with better EP per stamina will come soon.
Without any slayers I think 400K is almost imposible,
To get 600K EP takes atleast 2 slayers = p2w imo.