This should be more of a question is why can't relic unlike other companies offer small tweaks to stat changes instead of using a sledge hammer. Slight tweaks and test till the sweet spot is found. Honestly some of the changes don't require a pro to see is way to excessive.
I think the main problem is with all 5 armies and the huge power creep that the new armies have brought to the table, relic no longer has a clear idea of where all units power levels should be. This leads for lack of a better phrase to knee jerk reactions to try and bring units back in line one way or another.
My personal opinion is that relic need to stop look at each units place on the power curve, and instead look at the power curve its self. For example how powerful should rocket artillery be. Should they be able to wipe squads every time it is fired, or on some time, etc. Because i think relic has lost this.