I was not fan of frost comps, but I was tired a bit on Valeera-Malfurion comps and thought on counters. So I geared Ice Block for Jaina recently and this become my first comp I got 8000+ MMR. Lich King on start is good against any speed manipulation comps, like Valeera or Nature, I usually take him when see 2+ greens on opponent side. However I have a feeling that Tirion is better on all other matchups, it gives Jaina 1-2 more turns to live against melee opponents and its deathrattle buff is very strong for Illidan or LK. For now this Frost comp good against anything I see, the most difficult matches are against Holy builds.