Note: I don't have actual numbers for Ice defenses or fighting pool at hand from test server, this is going on the earliest numbers I've read.
I've had my Ice tanker since long before stackable armors. I've done every TF and trial and most story arcs with her as the primary tank. I've taken her on test as well. And through all that, the biggest problem I've always faced are the unreliability of defense, and endurance problems.
Defense Issues:
With defense, it's possible to go through a mob and not get touched, or to get pummeled completely. All depends on how the dice roll in your favor. Personally I took tough from the fighting set to give me more survivability in the face of opponents with high accuracy AND high dmg. Having one or the other never really bothered me too much. Avs and monsters and upper level bosses are the biggest issues. Without some type of resistance, we'll always eventually be one-shotted by an Arch-Villain, which I don't think any tanker should be.
However, the problem is that if the developers DO give us more resistances from permafrost, say even 5 %, we have the potential to become too strong. 5% turns into over 10% after enhancements, which can get up to 30 after tough if you choose it. (this is based on a guess at tough's I5 value being 10%)
This gives you a tanker who can potentially floor the tohit of any foe, leaving a 5% chance of anything hitting them, and then adding 30% resistance to anything that does hit them. If you then take into account hoarfrost, the atlas medallion and freedom phalanx, you have a tanker who can potentially outclass any other aside from invuln during Unstoppable (which pretty much nothing can outclass).
Since taking tough, I've never been one-shotted. If the numbers say we need more resistance, I'll be happy to take it. But I'm afraid that I just don't need it if it's going to be taken away once people start building defensive giants with heavy resistance.
I think a balance of defense and resistance would help, but I like my high defense. I don't want to sacrifice it for resistance if I don't have to.
Endurance Issues:
This is much simpler. many of the endurance costs are okay, but frozen armor and icicles cost too much for what they're worth to me in defense and offense. After keeping it for 50 levels, I finally ditched icicles in favor of more balanced endurance costs. On live, I run only wet ice, chilling embrace, tough, foc. acc., and energy absorbtion against even levels foes and turned on frozen armor and glacial when i run into something tougher such as large mobs, multiple bosses, or AVs.
With I5, I need to keep most of them running full time which causes more end concerns so that I can't afford foc. acc. unless Conserve Power is running, and I feel that the extra accuracy is needed in the upper levels if we're to rely on punchvoke AT ALL, which is inconsistent at best.
Over all, I've only spent a few hours on test, but most of my concerns are the same as they've always been. Balancing the Ice endurance cost, and making the defenses more reliable without making Ice too strong. The bone we've wanted to be thrown our way for so long could turn Ice tankers into walking caltrops, that's harder to kill than a cockroach.