I went to level 145 in 10 days by soloing my ice mage. My attunement is 42/30 and my shards and blast are both 35/30. My eshield is at 30/30 and I have lure nearly at max at 29/30. My ice magic is maxed at 1530. Those are the only skills I have invested in. I have seen posts here which indicate that freeze is also a good investment but, at this point, I am unwilling to sacrifice damage for freezing especially considering that they unfreeze the second you cast on them anyhow. The goal should be fast killing, not delaying the kill by freezing them in place.
That being said, I will admit that the process would have been much slower if I were running a low end build. My clan has kept me in the best gear for my level that we could muster plus I run constantly on super combo and heroic combo elixirs and I keep about 10,000 restos in my inventory for healing. To speed up my fights i have around 3000 sigils to keep me healed after battle. Without these advantages, it would be much slower. I only play an average of 4 hours on work days and 12 hours when I am off work so I don't have a load of time invested. If I could have hammered out 8 hours a day or more, I could be at level 180ish by now.
Near the end of the boggan tunnels, I am finding it faster (or maybe just easier) to level in a group with a single tank player. It prevents me from needing to keep my shield up. I keep my health around 2200 hit points and my focus is at 1037. Both shards and blast do 4000 to 5000 damage per cast on average. Even with restos I can get overwhelmed at times when soloing and trying to fight off four 3* plus mobs at once. Without restos, you might be able to do a 2 party group with a druid. I think 3 or more in a group would lower the exp to the point where you'd still be faster soloing . To be honest, I'm not sure that even 2 in a group speeds up the leveling process. I can still tank fairly well solo on combos. The fact that two make it easier could just be tricking me into believing it's faster. The biggest nuisance I am running into in Carrowmore is the damage delay when casting spells. This glitch will sometimes cause you to be killed by mobs who are already dead, technically. It's also harder to pull individual boggans out of the group here because, many times, the others swarm you when you try pulling one of their comrads.
If you are going to solo level an ice mage quickly be prepared to make a serious investment. I honestly don't believe that there are enough skill points available at these levels to create a hybrid which would be effective on its own. Of course, I am still a noob so I haven't had an opportunity to test that theory.
223+ Ice Mage