"One of the easier hardmodes" - huge mistake. After failing to heed the warning of others, my guild fell into the trap: the biggest mistake a 2/13 heroic guild can make is trying Conclave next. Conclave drops terrible rewards for a lot of time investment. Go to heroic Maloriak (9 pieces of loot) or heroic Atramedes (very easy).
Also, this guide lacks a lot of useful information:
First, the AoE from the adds doesn't just hit significantly harder - it's lethal. A single tick will kill most raid members. Kiting them is the only option, which is very different from the normal mode. When Toxic Spores gets close in the timer, you must have everyone focusing on avoiding them. In the normal mode, kiting the adds is not optional because Anshal heals percent-based per add alive.
Second, the Wind Blast becomes lethal. Getting hit by Wind Blast dishes out ~100k damage. In 90% of cases, you will die getting hit by a single tick of Wind Blast. For this reason, it's strongly recommended that everyone use movement speed increasing abilities and get near the boss. If you stay near the boss, the amount you need to move is much less. Melee are ideal, but can get unlucky and taken out of melee range by tornado's at critical moments. Healer wise, priests are best with the ability to bubble before Storm Shield, use Prayer of Healing for powerful group healing, and Body and Soul to help avoid Wind Blast.
Lastly, the damage is extreme rather than "pathetic" like it was before. Tanks will need cooldowns for any Permafrost above 5 stacks. You'll want to coordinate Aura Mastery and raid-wide damage reducing cooldowns while stacking up to take advantage of healing cooldowns at Nezir. Not only that, but the frost patches now stack a debuff rather than providing an aura-type effect. Similar to heroic Rotface, every tick slows your movement speed by 20%. At 5 stacks, you will be stuck and will quickly die. To counter this, start spreading out with about 3-4 seconds left on Nezir's Ultimate. Oh, and your tank will need to rotate cooldowns on the plant platform. Anshal will hit for 250-300k unmitigated for the 15 seconds after his ult ends.