Source

Basically, Bio becomes Bio II at level 26, and is now instant cast. But, it has potency of 35 still (so, it's weaker than Bio). Now you only have two DoTs, and Bane was given the same treatment as Holy (100% potency on the first, then 80% on second, 60% on third, etc, down to 20% minimum). Especially because our DoTs were already reduced by over 30% (and not to mention the loss of Aero for single-target), multi-target damage will be very low compared to what it was in the past. (oh, and Shadow flare is on a 60s CD now. Miasma II/Blizzard II gone as well!)

I guess it helps brings things closer in terms of balance, but it really sucks for solo/duo content :c