Tier 1- Block: Being thrall can be the front liner in a battle or a finisher, block comes in handy against everyone except Lili, Rhegar, Chen and Jaina. I don't like Rolling Thunder or Seasoned marksmen as I try not to stay in the middle of a fight long enough to have to use basic attacks against heros.

Tier 2- Spirit Journey: Another great counter to pokers like Li ming. The range is great and a good counter for Nova and Zera who pro players know how get in and get out quick. The rest of the uses are already known for finishing off a low health hero or keeping an Illidan in place long to kill em quick. Envenom is an OK choice, but I rarely use it, but i'd put it as a 3rd choice with Ride the Lightning as the 2nd best.

Tier 3- Wind Shear: This is where Thrall gets most of his healing from. By now your frostwolf stacks should be getting to 3 pretty quick and considering you have other healing options, it shouldn't be an issue. But If your laning without a healer, that Clutch heal from is needed. The 4 second countdown might now mean a lot, but it'll give you more time to stay in fights and keep getting those stacks and keep healing. Nothing else here except stone wolfs, but that extra .5 seconds isn't really a game changer to me.

Tier 4- EARTHQUAKE: The triple threat of Ultimates in the game. It's an escape for when your team pushes too far, It's a slow for the enemy when they are bunched up and the damage is good enough that in the right circumstance and good timing, it could be an instant wipe of the other team. This is the main skill I get complaints with in Hero League, because it's not Sundering. It combos well with every AOE hero Ult (Jaina, Kael'Thas(both of his Ults), ETC, Sylvanas, ect).

Tier 5- Grace of Air: Another Stack builder upper. Quick and easy to keep those heals rolling in and up to this point, should be healing for around 500 health.

Tier 6- Tempest Fury: That DPS is getting crazy now and Tempest Is the icing on the cake. By now Thrall can solo every camp (except boss) and solo most basic Heros. I've Solo'd Lili and Rhegar numerous of times this late in the game and even Chen twice. Another Option is Restless Wolves, but its only good if your behind and need to focus on AOE people like Jaina And Kael.

Tier 7: The most Versatile set in the bunch. Bolt is good, but I never liked it because I think it should reset Ult too (i know, making it OP), and Thrall doesn't really need to reset his abilities on the fly. So there Nexus Blades and Earthen Shields. Both can be picked with no regret. Shields for when you have an ETC, Kael, Jaina on your team. Nexus blades when you want to run through half the other team with 400 DPS (insane on a single target).