I think both LBs are fine when it comes to their design/function. SAM is the easiest to counter once you begin to pay closer attention to enemy LB gauges and player SFX. My only gripe is getting the chiten debuff if I hit the SAM with an AoE, even if I am not focusing them directly which ruins part of the counterplay behind it. If they just changed that I would personally think its fine the way it is. Same with NIN's LB, since it's something they can't easily abuse by themselves and is only really effective in a team fight. Only real gripe with it is the range it has, if they capped it by half I feel like it wouldn't be as egregious.

As for their overall kits I think they are fine. NIN has the strength of having an incredibly versatile kit, but with the drawback of it been a bit infrequent. The way Kissatsu is designed makes it able to adapt to whatever situation the NIN is in, but limits the NIN to not be able to be able to frequently adapt or abuse abilities. For SAM I don't think their kit is that bad either, the Ogi and Midare are telegraphed enough to where you can counter them in specific scenarios. And I don't think their sustain is that bad either, Chiten is good but besides that it doesn't feel incredibly bad either.