Ran 42 on Tier 2 earlier today. Had a full 5* jelly gear and the run went very smoothly. I died a few times due to carelessness, the damage is about what you expect for Tier 2, but with more of a say, Tier 3 chaotic flavor? There is a bunch going on, but it isn't as straightforward as clockworks tier 3 or as hard as say, SL. I think most tier 3 people will find it easy to solo, and most true tier 2 players will find it somewhat challenging. The reward payout was intense. I like the mix of poison/fire and the flavor-plot.
My only gripe is that these seem to be for the sake of running something difficult, rather than actually for a point. You can't farm things for drops or get item drops, so other than the prestige, I really don't know why people might run this constantly, as it is harder than the normal daily runs.

Heart of Ice:
2 bugs: first arena I literally watched a devilite slide backwards doing the moonwalk to an overseer. I thought it was lag, but I was hitting things and doing damage normally. I really don't think it was lag. I was shooting it with my DA, and the damage seemed to be normal. After talking to the overseer, he dropped.
The six-square area the Trojans get hung up on really bad. I had one stuck in a corner not doing anything for what seemed like forever. No charging, no nothing, with his back to the wall. I got frustrated and left and eventually he wandered out, but I noticed the same behavior in the last (?) arena, similar to how zombies get hung up on corners, this one was hung up on what seemed like the corner of the gate. I walked up to him to try to get him to swing/charge, and I got nothing. I was able to squeeze behind him and kill him, however.

The freezing orb things in this level are INSANE in the beginning and then there is BARELY for the rest of the level. Is this intentional? I had like eight of them swarming me in the first gates-locks-and-fiends area and then the further I got into the level they would only show up occasionally. I think how they spawn needs to be evened out a bit so they are more consistent throughout the first level of Heart of Ice.

Is the boss supposed to be so easy? I found his spawns to be more of a concern than the boss himself.

Things I liked: I loved Heart of Ice more than 42. It is amazing. I want more 'frost' themed items (frost valk armor for us gals please) and it was absolutely beautiful. The boss was really cool, I really enjoyed that. I think a lot of people will find this challenging due to the ice/fiend theme combo.