Mono-Red Sligh's creatures are almost entirely 1-toughness (Mogg Fanatic, Grim Lavamancer, Ball Lightning) or 2/1s (Jackal Pup), so Pyroclasm sweeps their board for 2 mana and buys crucial time. Hydroblast counters a key red spell or destroys a key red permanent like Sulfuric Vortex, which otherwise burns you out on a clock you can't ignore. Daze and Mana Leak are too slow and tempo-negative against a deck already ahead on the damage race, so they come out for cheap sweeper effects. Race carefully with Basking Rootwalla and Wild Mongrel, and focus on controlling their early creatures rather than racing recklessly when you're behind on life.