If you really find it such a pain, just make a save, get a tacheon nuke, use it, memorise the foe's, reload, kill them.
(Usually with engies/rebuilders you can find them by memorising where the guardsposts/CC where, they tend to be there, at gates or near harvesters(which usually are guardspost positions). Cloaked
pointy foes tend to attack when you give them a vunerable target, use this to your advantage