Actually, The multiple combo trees seem to be set up that way on purpose. Take LNC, the combos from the front end up stunning the mob, which is very useful while soloing. The other combo Back-->Side--> Any is a lower accuracy/high damage combo, for when playing solely as a DD. Also, you can pull of the rear combo when soloing, as I think almost every martial class has a stun (bind in ARC case), allowing the movement to the correct point.

For example, build up 2500tp on LNC,
True Thrust --> Heavy Thrust --> move behind mob -->
Vorpal Thrust --> Side mob (should still be stunned) --> Impulse Drive --> Chaos Thrust.
Then pull off a True Thrust --> Leg Sweep --> Doomspike to stun the mob again while waiting for heavy thrust.