Losing Thunder is part of our DPS.
Losing Allagan Boots is also a stacking part of our DPS.
Bane "buff" is not really a buff. It still only hits 3 targets which makes the range boost insignificant. Rarely do I run into a situation where I can't spread my dots to all 3 other targets. Losing the chance at refreshing duration is a DPS loss.

Blizzard 2 is okay, it'd be nice to have without losing something else, but it doesn't make up for it. It's a slightly different version of Tri-Disaster.
Tri-Disaster: 3s cast, 2.5s recast, 266 mp, 25y range, 5y radius, 30 potency, 20s bind
Blizzard 2: 2s cast, 2.5s recast, 212 mp, 0y range, 5y radius, 50 potency, 4s bind, does not grant umbral ice
Miasma 2: Instant cast, 2.5s recast, 186 mp, 0y range, 5y radius, 20 potency, 10 potency over 15s
So Blizzard 2 is a little stronger but requires you be in melee range and has a shorter bind time while Tri-Disaster has a longer cast time and can be cast at a distance and has a longer duration but is lower damage. For comparison's sake I threw our close range aoe up there too.
It's redundant to have both spells.