UR Aggro is a fast tempo deck built around cheap creatures (Elusive Otter, Pompous Battlemage, Slickshot Show-Off) and Burst Lightning as both removal and reach, so Meltstrider's Resolve lets your creatures fight down their small threats before they grow out of control. Surrak, Elusive Hunter is a resilient 4/3 trampler that survives Burst Lightning's unkicked 2 damage and can't be countered, making it a strong roadblock against their tempo plan. Shared Roots and Earthbender Ascension are too slow and don't affect the board, so cut them in favor of combat interaction and a hard-to-kill threat that can race or stabilize against their aggression.