My luck is 10 and I use energy weapons.For some time I mainly used laser weapons and I would constantly disintegrate things,some times I didnt even have to shot them in the face and they would still turn to ash,then I started using a plasma rifle,even though I was still scoring critical hits things would turn to goo only like 4 or 5 times out of about 30 things killed.I never used plasma on Fallout 3 so I dont know what it was like.Is it like this for anyone else?

If it makes any difference, the killing shot has to be a critical hit in order for enemies to be diintegrated/goo-ified

Depends on the weapon, but yeah, I'm getting this too on my EW character. It happens more if you are using a beam splitter on your Laser Rifle or if you're using a Tri-Beam Laser Rifle, and it's relatively common with the Laser RCW because just one of the many little shots that gets through needs to crit for it to be a likely killing blow. If your character is built anything like mine, your chance to crit might look something like....

10 Luck + 5 (1st Recon Beret) + 5 (Finesse) = 20% base crit chance
x2 crit multiplier with Plasma Rifles = 40% chance to crit
x2.5 crit multiplier with Pew Pew = 50% chance to crit
x1.5 crit multipler with Tri Beam Laser Rifle = 30% chance to crit with each beam outside VATS (so if all 3 beams hit, very good chance of a crit)

If you have Better Criticals, you're also doing another 50% damage on top of the crit damage. Since the crit damage is usually worth another whole shot or so, you're potentially looking at up to 250% damage, depending on the gun (plus any damage bonuses from max charging your ammo...). A single critical hit on a sufficiently powerful energy weapon is enough to kill many enemies, and with crit chances so high that it only takes 2-3 shots before you see one, that means that almost every enemy tough enough to survive more than one shot is going to die from a crit.