There probably are a few factors resulting into them needing to simplify the jobs...
The needs of controller players vs. keyboard & mouse usually favor the keyboard and mouse controls in terms of performance and speed and amount of inputs and ability to react to mechanics, quickly toggling through large target pools, and maintain DPS/HPS output. This result to button bloat issues for controllers that result in actions being pruned that parties may expect to be used like palisade and cover, and very different reactions to increasing or decreasing the number of player actions.
It might just also be that reducing the number of actions that players are expected to use through simplification: players will have more time to deal with mechanics instead of their parse, which could allow the dev team to focus on more mechanically intensive encounters