Holy Speed Manipulation

This is more-or-less a collection of my favorite Mercs, but I also think it can be a decent composition in its own right. They have a focus on slowing enemies down to eventually overwhelm the opponent, with side ventures of Holy interactions, healing, and general tanking:

• Speed manipulation comes in the form of The Lich King's Frostbite (with Frostmourne to boot), two of Cairne's abilities, Diablo's Doom Charge, and Uther's Hammer of Justice.
• Holy comes from Xyrella, Tirion, and Uther. Blessing of Luminance + Judgment of Humility + Avenging Wrath is a solid combo turn.
• Healing comes from Uther's Blessing of Protection, Cairne's Ancestral Uppercut, The Lich King's Death Coil, and Xyrella's Flash Heal.
• Tanking comes from The Lich King with a Freezing-Taunt, Cairne's Taunt, and Uther's Blessing of Protection providing Taunt without a Cooldown. There's also Xyrella and Tirion's ability to neuter Attackers, mitigating damage.

Slow 'em down, then pop off Diablo's Fire Stomp for massive damage.