The 5man gametype in general is extremist with its metas; you keep seeing the same handful of specs on and on for months and for an entire patch or even an entire expansion; this is because the game has 12 classes and dozens of specs so even if 20man can still have metas: they are extremely diminished there because even if you stack 5 druids: you'll still have room for others' utilites and passives at the very least.
This is why the 5man gametype should be reduced by just releasing a couple of instances less; make those instances exclusive 10man mythic raids; people love it and it would not disrupt the competition in 20man instances and it's a nice middle ground between the extremist metas of a 5man and the more complete 20man gametype.