That's the way classic works. You are 'mouselocked' during the swing, but can otherwise move and strafe while swinging and I find that works well enough for attacking and backpedaling to avoid getting hit. I usually don't have trouble keeping the view focused on enemies, probably due to lots of experience with classic. DFU allows changing the threshold of the mouse movement required to swing weapons - I did find the default values to be off for my mouse and had to adjust it to match classic behavior - the default settings may be a reason why there is difficulty in keeping focus on enemies using this method of attack.
I can understand why people prefer the simpler click to attack - DFU has better enemy behavior which makes the early game expose the combat limitations. I would say that the DFU's early game with enhanced AI is significantly harder than classic.
Attack type becomes unimportant after gaining enough weapon skill - at that point (i.e. after the early game period), click to attack is objectively better but I find it less satisfying.