best gem setup for a 6L reave?

If you have Carcass Jack in your build (gear-wise), then I highly recommend Concentrated Effect. Carcass Jack to some extent nullifies the drawback from CE, and you get an 12% Increased Area Damage, which is more DPS for Reave. Like Melee physical damage and multistrike, Concentrated Effect gives you "more" damage in the form of AoE. That "more" damage is multiplicative, so your DPS is boosted by a lot moreso than the likes of Faster Attacks or Added Fire. Now if you do not have or do not intend to use Carcass Jack, then CE will hurt you AoE-wise.


You mentioned that you are doing crit build, then it would make sense to include either increased critical strike (increases your DPS, but more importantly your crit chance) or increased critical damage (increases your DPS......when you crit). It depends on what you have in your build, if your crit chance is high, go crit damage, or if your crit damage is high, go crit chance.


Now for the last spot, added fire damage would benefit you more if you have a lot of physical damage, like I mean a lot, when you gain that extra fire damage from a certain % physical damage, you actually get a big boost. As for Faster attacks, more attack speeds helps. Up to you at this point.