Behemoth may cost two more mana than Crucible of Worlds or Ramunap Excavator, but it also blocks all but the biggest creatures
In addition to this army of massive creatures, the deck features a number of utility spells including mana rocks, numerous removal spells, ramp spells, counter effects, etc
Another reason to sideboard out Thoughtseize is if no specific card matters
I don't think there's an issue with moving up the power scale provided you are playing decks that fit into your playgroup or meta
Together with Hibernation Sliver the deck could have good answers to all anti-creature effects other than permanent barricades and have enough copies to make sure that each Sliver wave contained at least one
After a run of unusual or experimental sets, Dragonstorm felt familiar in the best way