Hearthpwn

I personally use Dawngrasp, Jaina, and Lich King as my openers, Tavish, Diablo, and Cairne as my Bench. Still working on fully maxing the openers, and haven't really focused on Cairne yet, but I digress. The Dawngrasp, Jaina, Lich King team is super strong because Jaina's middle Ability buffs Frost damage for Dawngrasp, herself, AND Lich King's Helm Equipment, making the Helm a BETTER choice than Frostmourne for a team running Jaina.

Additionally, most opponents will focus on Jaina or on Dawngrasp because they SEEM to be the real threats (while Lich King is one too because of the Helm), but Jaina has her Ice Block Talisman and Dawngrasp has his Deathrattle Equipment, making focusing them more difficult to handle.

Cairne is there for obvious Speed Buffs and moreso the AOE Speed Debuff, so that Diablo's middle ability triggers 4 times (between Dawngrasp, Cairne, and Lich King all slowing your opponent's abilities). Tavish is included for obvious anti-Caster value.