I think he is refering to the fact that Skarm + Bliss + Clops + Pert would be almost an impossible unit for this team to break but then again, I like how he uses Zam to draw in Blissey so he can finish it with Dugtrio, and I also like lefties lax with fire blast for skarm. I do agree on HP Grass somewhere, perhaps even on raikou? I would think of it this way, you have 2 pretty good special attackers with ice punch, and one of them should be alive when blissey is dead thanks to dugtrio. So hp ice on raikou seems like it would be good for mence (but tbolt does a shitload anyway), breloom (not too worried about this, it cant switch into anything at all and raikou can block spore / leech seed anyway meaning all it can do is probably focus punch which you block by just attacking), and a few other pokemon like bulky grounds. But HP grass provides the same coverage on bulky grounds, mence and loom are already covered, but swampert isnt. Since swampert is a pretty common switch in to raikou it gives you the perfect chance to cm again. Usually they will switch out to scout for hp grass first meaning when you see a pert, you should cm (if you have the sub, attack if you dont). that basically means you could get 2 free calm minds and then a dead swampert. sweet deal if you ask me.
I like the heavy offense and suicide approach to the team.