I get to talk more often with tough because of the US offsite chat during games (which is less crowded and more individual conversation oriented than the 40 man scrum known as USA chat).
I think the problem tough has with his scrubs specifically are that they are legitimately scrubs.  The sub 15% shooting in most games of importance isn't just a sign that he is a bench player, it's a sign that his JS was probably in and around 2-3 (talking in specific about his player lofton.
The guys on my bench in D.IV are not drastically different than the guys that my previously owned team had in D.III 
Bench Guy 1:
7/1/6/6/6/7   5/6/7/7  3/1  with a 3.5k salary.  Purchased for under 5k on the TL.  I can use him about anywhere.
Bench Guy 2: 
3/5/5/4/7/5   8/6/7/4  3/8  with a 3.5k salary.  Purchased for under 5k on the TL.  I can use him primarily at PF and C, but if needed could also play SF in given offensive/defensive schemes as a bench player.
Bench Guy 3: 
7/8/6/9/6/5   3/6/3/6  6/6 with a 3.0k salary.  Purchased for under 6k on the TL.  Primarily a SG/SF depending on what scheme i run, and starts the scrim games.
Lets call bench guy 3 the Guard sub, and Bench guy 2 the big sub.  I think your problem is you lack about 800-900 salary in comparison, and with regards to specific builds, you probably asked lofton, who appeared to be a 3/3/7/6/5/6  2/4/6/x type of build to play against the top team in your division who probably had double digits in most guard attributes and considerable salary as well. Not only can he never really get a good opportunity to take a decent shot against what was likely a 13+ OD rating, but he also probably was close to doubled in JS vs his OD rating.  A bench guy with 7 JS and 7 OD may only fair a point spread of +4 to +7 better, but if you upgrade each position by +4 you aren't looking at a 1 point loss.
TL:DR - I think you need to spend about 15k on the backend of your bench for situations like you ran into this season as far as TL costs go, and probably 10-12k combined on their salaried costs.  I like having an 11 man roster, with 5 starters, a guard and a big for backup, and mostly the 3-5k variety players to round it out.