Providing that they are low in numbers, a -2 leader does not seem outrageous.
Remembering bits of the original SL design notes, they stressed that not every squad leader was represented. So, any leader is a cut above the average.
This is my interpretation:
+1: Idiots and higher ups who have forgotten their low level stuff and drives the junior officers to madness with medling.
0: An Efficient leader who puts in a good solid reliable performance. Nothing fancy but usually gets the job done. Troops trust him.
-1: As a 0 but has good tactical sense and a few tricks learnt from experience. Can show a fair bit of initiative. Troops both trust and admire him.
-2: Always on the go, in the thick of it, well honed combat skills and destined for higher things. If he survives! Troops either regard him as the second coming or a "our guts his glory" lunatic.
-3: Certified, either as a lunatic or genius. Troops will at times regard his leadership as a, likely posthumous, medal winning time.
So 0 or -1, no problems. How many -2? I would say 1/4 to 1/10 of a side's leaders. In an action mentions actions by a particular NCO/officer then throw one in. If you have much more than a 'fat' company then consider one. A 10-3 would need a certified film clip of said officer walking on water. The Chapter H allocation makes -2 leaders rare, you would have to have 4 x 8-0, 3 x 8-1, 2 x 9-1 to get your 1 x 9-2, only 1 in 10.
My experience is that amongst a decent number of other weaker leaders a -2 often does little better than them. Yes a good DR with a -2 DRM can wreak great damage, but not as often as you might expect. Of course 1 x 10-2, 2 x 9-2 commanding 6 squads is another matter. Like in good cooking, sprinkle sparingly.