Multiple Projectiles and DPS (

So I'm probably missing something obvious here, but Lesser Multiple Projectiles seems to be hursting my DPS more than it should.

So I have a level 11 LMP. It says "20% increased projectile damage", and "30% less projectile damage". Fair enough.

Without the gem linked my Ice Spear Spell Totem does 373DPS.

With the gem in, however, it does 278DPS (Per projectile).

That's about a 30% reduction in DPS.

What happened to my "20% increased projectile damage"?