Well.. to be honest.. i really don't know yet what the cause of this is.. but here it goes:
Using Avalanche - Tectonic Rift (up to 3 Charges of Avalanche stored) after some playtime it always happens that i kind of get infinite charges.. well not exactly.. but the just used 3rd charge refreshes immediately after using any fury spender skill.
If it happens, you must not use more then the 3rd charge.. so.. back to 2 charges - using any fury spender (WW works really well..) will instantly bring back your 3rd charge.
Meaning you can cast Avalanche every second.. over and over again.. you just have to keep your eye on the charge counter and hit Avalanche right after you got your 3rd charge back.
If you drop below 2 charges.. bug is gone.. but will be back after some time.
As is said.. i don't know the cause of it.. but it happens all the time.. sometimes its right from the start and sometimes it takes a couple of minutes until you get the bug.
If you get it.. as long as you don't fall below 2 charges you can spam Avalanche one after another..
in short:
-check for bug from time to time
-bug active:
[-use 3rd charge
-use any fury spender (as i said.. WW is awesome for this)
-3rd charge rdy again] -> repeat