However, I'm worry that it may be super hard for me to complete my RM hard quest :/ (I'm full colo)
Would be appreciate if they can nerf Ratmaster Hard mode a bit in my opinion.
RM H is fine as it is. It takes coordination and for people to know the fight instead of people being carried. Ratmaster is probably the most fun raid boss out in game at the moment.
Downing the Rat after multiple hours will hold such satisfaction which truly makes it the obstacle to enter AoD a true challenge.