Posted on 17 May 13 at 07:13
If memory serves, his thugs respawn after you take the last of them out.
It's a matter of thinning the herd, then swooping in to lay a hit on Harvey, then disappearing again. Don't try to take him out in one attack. You need to hit him and disappear. 4 times total if I remember correctly.
If it's the thugs themselves that are causing you the drama, your best bet is to know where to lie in wait. The best prowling areas are the corridor upstairs (with the grill that allows you to cling to the ceiling) and the corridor downstairs with the grill in the floor. It's relatively easy to take 1 or more thugs out in each area without getting detected, and that should open up attack avenues on Harvey.