First, with field spec I can no longer advise setting up builds that compliment PvP and PvE. It's fairly inexpensive and well worth the credits/cartel coins. The main reason for this being is you will not be able to optimize your build to it's real potential. There are talents for PvP: Trip Shot, Heads Up, Kneecappin' and there are PvE talents: Foxhole that just don't work well in all in scenarios.
That being said, Leg Shot is one of our best utilities! I use it ALL the time. With the addition of Kneecappin' it is, IMO, one of our best and most crucial talents in PvP. If they blow their CD to break Leg Shot then you should win the fight period. You need to bring LS into your PvP rotation and hotkey it.
But like I stated above Leg Shot is not helpful in PvE so your build would be ruined to invest in it when you are not in a WZ. Same with Diversion since it does not work on Bosses.
My suggestion: Invest in Field Spec. Optimize your builds for your goal.