Kalal is the grandmaster of slow-paced, ranged combat. If the game is getting into a slow pace, Kalal's entry can change the odds greatly in Tacullu's favor. She may seem relatively expensive, but with Kalal, losing slow-paced, ranged combat seems impossible. She can keep enemy melee units at bay while attacking with four ranged dice, or protect herself with cheap friendly units, that can then attack also after she puts them in position, altogether doing lots of damage from a single flank and not leaving a good counterattack opportunity for the opponent.
Trying to keep a slow game versus Kalal may be the same as conceding.