Abilities that land after the "ferocity" buff is activated (clipping) and abilities that are activated just before ferocity ends are both affected by ferocity. Because of this "4" abilities can be buffed in a single ferocity window when carnage's berserk is used, though this requires a lot of practice to be done reliably. Due to this nature of ferocity, "3" abilities can be buffed in a ferocity window when the carnage berserk is not utilized without clipping. Because of this, your proposed changes to carnage will be a massive nerf because carnage is being dropped from 7 buffed abilities every two ferocity windows to 4 buffed abilities every two ferocity windows.
Another issue i have with these changes is that it removes the exciting and original play style of carnage and replaces it with button mashing. If you must make a change to the carnage discipline, at least change it to something thats interesting to play. Be creative. We have enough stack based classes .
I would advice you hold off any changes until you are completely familiar with how the carnage discipline works.