Operative Lawson's uniform is very official: Head on up there near Rodam Expeditions look at your map to find him talking to someone on a communicator. If Shepard is a Soldier or an Infiltrator, you can cover long-range combat, since both classes can use sniper rifles, but if Shepard is a Soldier, you can additionally cover for the lack of combat powers with the addition of a shotgun which covers very short range. It also results in the spurned party no longer talking to the Commander even if they part ways amicably. It's generally a good idea to bring along a Biotic to all of your loyalty quests. As much as she might seem ideal for a Renegade romance she's actually best suited for a Paragon. The perks of having a secretary eh?
Mordin is an excellent choice against krogan and vorcha enemies primarily due to Incinerate, which burns very quickly through armor and permanently stops health regeneration.
Keep on moving forward, taking out the troops that pop up between the crates as well as inside of the shipping crates. The mech is its usual powerhouse self but the humans all have shields making a fight against them all the more dangerous. Basically, do not use this pairing where there are Blood Pack or a lot of krogan. However should you not wish to take the risk it's possible to refuse to sleep with her. Only test is contact with seeker swarms. If you'd rather take shields down with weapons fire than Overload, you may want to consider Zaeed as a replacement for Garrus since they carry the same weapons and Zaeed boasts greater damage output along with Disruptor Ammo. Agreed, I found Overload and Warp very handy on Insanity.