The same guy has a vid out where they play double boomkin + enhance in 3s and literally 1 shot someone. Not very familiar with boomkins myself, but whenever I tried them I had the idea they were fairly complex to manage due to being so heavily proc dependant (which is far from being an educated guess). All I know is that if you play as dps with a boomkin in 2s, it feels as if you play with a healer that has sick dps.

On paper they have a lot of + for multiboxing 4 of them, no idea if its even possible to get it working though.