I'm almost to the end game sequence on my third time through, LS all 3 times. The first two times I used a lot of force wave at the end of the game. This third time, I got force storm and death field because I thought they would be fun.
Force Storm vs. Force Wave
Seems like force storm is 79% more effective than force wave when using force potency if everyone is within 10m.
With force storm, you dish out 1D6 times your level which averages out to be 3.5 x your level. With the extra 30% damage from force potency you get 4.55 x your level. The cost for me (Light Mastery) is 46.8 FP per use (20+19 plus an extra 20% for force potency). The end result is 0.097 HP per level per FP.
With force wave, you dish out only 1.5 times your level so you're at 1.5 vs. 3.5 for force storm. An extra 30% gives you 1.95 HP per level. The cost is 36 FP per use (25+5 with an extra 20%) resulting in 0.054 HP per level per FP. Comparing 0.097 to 0.054, force storm is 79% more effective.
So the winner is force storm even for lightsiders. It's true that wave stuns your opponents but do you really want to stun them when they could be dead?
Master Heal vs. Death Field
I thought death field would be fun but I found that when I was attacking I'd still get injured and healing myself with Death Field noticeably drained my FP.
Master heal heals 15 HP + chrisma & wisdom modifiers plus 2 HP per level at a cost of 14 (25-11).
Death Field gives you 1D4 times your level which averages out to be 2.5 HP per level. The extra 0.5 HP per level isn't much more than the 2 HP per level you get from Master Heal and is usually negated by the other master heal modifiers. Plus the cost is 49 FP for me (25+24). I stopped using death field and just force storm. Usually they're all dead before I'm injured so I don't even have to heal myself during battle unless I'm trying out wimpy weapons or no weapons.
Conclusion
I've gotten a number of other DS powers but it seems like force storm is the only really worthwhile one for now. Seems like I'll end up using force enlightenment, master heal, and force storm for the end game. I don't play DS because I can't be that cruel to innocents but I have to say I like feeling the power of the Dark Side! Reveling in the dark side as a light sider makes me feel like Mace Windu
What are your favorite Force Powers? Do you use any opposite aligment powers?