Amalgam is healthy and a disease for Battlegrounds at the same time. As long as it's around murloc or menagerie comps will always prevail. But it's necessary for other tribes, especially demons and beasts to have access to divine shield + poisonous as well. It doesn't matter if your massive Annihilan Battlemaster sits on the board with 250+ health as long as your opponent has multiple poisonous minions on his side.
In regards to Murlocs, it just gets tiresome really fast. They went too far with the recent buffs so the mid game devolved into "who can stack their murlocs first?" and if they aren't available everyone switches to mechs (say hi to Cobalt Guardian + Replicating Menace). That's another problem I'd like to see adressed in a further update. For now, there is no counterplay to a bunch of tokens, especially when they also support a tier 3 minion which is presumably more powerful than any other minion at this level (even outperforms some of the tier 4 ones)