In duels if you have All together now treasure it reads"Your battlecry cards cost 1 less but not less than (1)" but crabrider still costs 2 even though it reads “Battlecry: Gain windfury this turn only”
TL:DR crabrider doesnt count as battlecry minion.
This is a problem in Standard too. Crabrider is currently not flagged as a Battlecry minion.