Go into the menu => documents => weapons. Though I haven't exactly heard about
that kind of tertiary fire either, there's a snippet in there about holding down R1 to make the missile seek. And sure enough, the widowmaker I fought in Angel's Lair fell after just two hits, on hard mode no less, when I tried doing that, even though I didn't notice any visual difference. I could never kill any widowmaker without blowing all four missiles I could carry
and then throwing some other ammo after that, so I suppose it did something.
Oh and as for the rooftops, I've already tried that but without success -- while playing the campaign on hard mode, I just couldn't do it quickly enough. The Auger guys were sapping too much health off of me, but take too long to kill.
But anyway, you can just rush the first Chimera, head up the stairs and then just hop across, ignoring everything. If something's in your way, use the melee attack.
Drop down, run away from the Auger guys, blast the arc charger guy and his two standard Chimera friends with the arc charger's alternate fire (seeks targets and hurts all three of them at once). Run onward switching to the shotgun, let the leapers and the big grey guy have that (a close-up shotgun blast stuns the thing). The rooftop is where I lost patience, but I suppose if you have a rocket or two, or a clip worth of Hailstorm secondary fire, that would be a nice place to use them, otherwise a slowmo-sniper-headshot for the final Auger guy would be recommended. Then throw a couple of 'nades forward while you cross the plank and you
should make it.
At least two basic Chimera soldiers, a bunch of leapers and two Auger meanies would still be alive while you race to the subway station. Basically everything that spawns on the first roof, in the alley behind that, and anything that is stunned for long enough to just run past.
I'll try it on easy mode, and if the strategy needs fixing I'll send a memo
