I agree here, the realy long "rain down time" makes this skill kinda unusable. I combine avalanche and inferno, even the realy slow avalanche kills everthing even before inferno hits 1 time - even if i cast inferno as first.
Ofc it haves to give a disadvantage on this skill, coz its high base damage (more than each other spell!!)needs to be balanced out with something other that isnt as good as other skills.
But as i said it seems stupid to klick a single mob and w8 2 sec until he dies, leveling/killing last at least the double or tripple time, that it would least with a little fireball doing way way lower dmg -.- (imagine you do a sectret map, there the eneyms are not crowded, now you have to w8 2 sec for each.... realy everthing in the world kills faster..)