More of my own thoughts later in the expansion:

Healer and tank should compliment each other.

RSHM + Brew is excellent as RSHM brings a lot of utility, Brew brings the gap fillers such as a poison/disease dispel and a lot of mobility / stagger mechanic to smooth out healing.

MW + BDK would also be good because this is the inverse. BDK brings tons of utility and MW brings mobility and the big tank cooldown.

PROTW + RDRU will always be a good option.

I don't know PROTP so well but I imagine the best healer for PROTP is MW.

HPAL would probably want a tank that brings some mobility and big defensives and some utility so that sounds like PROTW.