Bit late chiming in here but maybe my input will help considering I did RSHM + PROTWAR + 3*BM for a few years in dungeon running. This is just my anecdotal over the years doing it.

PvE: Hunter can be very strong due to mobility. You shouldn't take too much damage with them if you keep them moving all the time. This is offset by all the utility you are leaving on the table if you took locks or shamans instead. Also, because I main a RSHM I found in the end hunter was just not the right option. Reason being the RSHM favors more stationary comps. I switched over to MW because it worked better with the hunters. Still, one misstep could end you.

PvP: Wow, Hunter is a horrible option for this. So mobility being a huge plus actually works against us multiboxers. In PvP you will be too busy to move the hunters around. For multiboxing PvP you want a very durable ball of death. DKs, Shamans, Locks are all superior options to a hunter ball with the lone exception of the opener. That's it though. In a real battle with give and take you want those extra heals and the utility. AF Locks can hit you without looking at you for most of what they do. Fears are an amazing CC that should always be used. A good combination of snares / fears and stuns are ideal. Demonic Gate is also great for your healer, especially shaman as people love to train shamans.

Incidentally for a long time I loathed my WLS because of all the changes to warriors. A lot of stuff I didn't like happened. So I abstained for most of Legion. I switched over to Unholy for a bit and prattled on with different class combos. Never really found something I liked. Hunters kinda died for me on mythics where movement was getting to me and the lack of heals made it difficult. I think the comp choices just didn't work well for me this expansion. Hopefully the next expansion addresses some of the glaring design problems.