In my 14th season, I had troll results but only 1-2 per season but never had a continual under-performing period (from whole my team, not only 1,2,3 players) except the last week- 10 last days of 12th period. I explain this from many injuries, had 5 reserves only and (good) players starting playing bad after healing-injured-healing again.
This whole period so far I was keep building (without rushing) so I don't think construction is relative.
As for win bonus, I think it's just a +1 (or 2,3,4) % from my experience but also when I asked with this old post, and many experienced forum members had a different approach - answers.
http://forum.topeleven.com/top-eleve...questions.html
That's my personal rule (because we didn't have so far a clear answer from game developer) :
If I ask (or read something) and there aren't clear/positive answers from many experienced forum members then there isn't an issue or else they would noticed that or it's a slight effect.