Are you killing the enemies with the burn? Its not the bullet or the blast that counts toward the catalyst. Its the burn. Heres an easy way of getting this done. Go into the Leviathan raid solo. Go to the flag room. Go post up on cups on the little catwalk thing and look down into dogs. There will be a bunch of cabal and phalanx. Shoot the phalanx shields to get the easy crits, then [u]head shot[/u] a FULL health legionnaire. Let it die to the burn. Wash rinse and repeat until done.