Never said its easy, but its doable. I'm glad you know what the dev's have in mind, I would love you to share some more of their thoughts, because some of the latest updates have me confused.
That won't stop any arcanes from soloing epics, you can be pretty sure of that. It will just make us think of a different strategy that is all.
And crit walls really do not matter for non-epic content (as has been mentioned many times already), you can pretty much instakill everything already with necro spells (yes,that includes Amrath).
Ice storm might work. Once it hits live it will be tested and figured out

There are other options for a soloing arcane too, just slower.
Mostly what I was saying is that its a nerf to firewall and arcane fire DPS (per SECOND, meaning you will get the same damage in a longer period of time), no matter how some people try to twist it.
Another problem might occur is with aggro - a few crit ticks on a mob not being hit by other party members can get you unwanted aggro. If you see that the wall is crit now, you will be prepared for that. You can't know if its random per tick. On the other hand, you can not reliably hold aggro with a wall that is random like that and will lose it to melees/arcanes regularly.
Edit: Can anyone write how this change affects Blade Barrier?