In 2.1 the loss of Thunder is replaced with the addition of Blizzard II for SMN. SMN was already the king of non-SR (speed run) AOE, now it's going to help close the gap on SR AOE when compared to other jobs. Before you had to cast Thunder individually on every target to maximize AOE DPS on 2-4 targets (which took up the entire time between your rotation). Now Thunder mutlicast is replaced with Blizzard II and it works very similarly to casting Ruin/Ruin II between DOTs in your rotation. You never really had enough time to cast Thunder on all 4 mobs between rotations.

Bio: Potency 40/tick Duration 18s (6 ticks) Total Potency = 240 (2-4)
Miasma: Potency 20 + Potency 35/tick Duration 24s (8 ticks) Total Potency = 300 (2-4)
Bio II: Potency 35/tick Duration 30s (10 ticks) Total Potency = 350 (2-4)
Shadow Flare: Potency 25/tick Duration 30s (10 ticks) Total Potency = 250 (ALL)
Miasma II: Potency 20 + Potency 10/tick 15s (5 ticks) Total potency = 70 (ALL)

Bane: Potency 0