With Blissey at an all time high in viability, Mawile comes in to absolutely demolish any of its weakened teammates. It's SD set plows through nearly any defensive switchin, and sucker allows it to clean up offensive teams. It no longer has to play 50/50 games with pult, so I think its more effective currently.
Combined with Mawile, I get a double priority offensive core which also means I don't need to run speed control and generally frees up the team. Spikes support makes Mawile even more ridiculously threatening, and its ability to draw in Blissey for Mawile to potentially take advantage of is great.
The rocker of choice, and facilitates easy switch ins for Mawile, due to have two Intimidates on the team. I chose smack down as my last move, since with Spikes on the team and Zapdos at an incredibly high usage, I'd want to scare it out of getting a defog off over toxicing it.
The fat special check of this team and we all know how good it is right now. It provides me with a great way of absorbing status and getting my threats in, as well as giving me twave support for Mawile to abuse. One great interaction is with Mega Latias, where if you twave it, Mawile is able to easily outspeed and kill it.
A terrific Rillaboom and Heatran answer all packed into one defog slot, since Lando is unable to handle both of these mons for any extended period of time.
I think Kyurem is terrific in this metagame, as its able to annoy Blissey while also having probably the most dominant matchup against rain of any pokemon in the tier. Blissey easily gets it in against mons like Toxapex, which it abuses to no end. It also appreciates the popularity of Zapdos, as it also abuses its presence on the field.