I shall only look at exploit weakness.
The formula is (DA*16+AP)*M.
1 DA is equivalent to 1 AP. This ultimately means, only grab AP gear if AP is a byproduct of the gear. This pretty much means get an alti and refine it. This should maximise your damage output for EW without compromising your damage for other DA only based skills.
Also note that DA can be buffed whilst AP cannot; given this, DA is definately the way to go.
As for LK, it buffs more percentage wise that DA does; given you have two luck buffs.
Give landmine is equally affected by DA and LK, a higher base luck will be more beneficial.
However, DA contributes more in EE, so a stacking into DA over LK is better for this skill.
Since EE is stronger than LM, damage wise, it is better to stack DA.
Basically when looking at balance, you should worry about the following criteria:
The damage formula of the skills; any stats they all have in common? Any stats unique to certain skills?
Which equips can be comped with these stats.
Which slots cannot?
Do you have survivability issues?
If so, which equip can you replace that maximizes your survivabilty without compromising your damage.
Yeah balance is a complicated thing.