Why is Dark/Samus at -1?
Samus is so slow that it seems like Cloud has virtually no lag on any of his aerials or grounded moves when they're spaced. Can't really approach since Climhazzard and Usmash are good anti-airs and Blade Beam just trades with missiles or baby CS so Samus can't force an approach. Can't fight up close or at mid range either since Cloud's Car Bumper Sword out ranges everything but Zair. Full CS hasn't been a threat to anyone since the projectile nerf.
What types of problems are good Samus players giving you?
I put Dark/Samus at -1 just because Cloud's biggest weakness is recovering to stage and I find that Dark/Samus can exploit this well. Her tether grab is very strong against Cloud since it can outrange a lot of his options and throw him off-stage. From there, nearly any attack from Dark/Samus could mean a stock.
I find that good Samus players are just very good at keeping cloud off of the stage, and while on the stage can rack up enough damage with a "hit n run" sort of playstyle to put cloud in a rough spot.
I do see what you're saying though, and maybe my personal bias has made me place her lower than she should be. I feel like I have a somewhat hard time against Samus in general. But I mean, that's the point of this thread, I want to broaden my perspective and perfect this matchup chart by sharing thoughts.