Been playing Samus for a bit. I agree that her nair is nerfed. But I also think it was taken out because the game isn't about shffl-ing. It's feels more about space control and reads. For air to ground, I found I've been using dair as it recovers just as you land from a short hop. I reserved bair and nair for horizontal air-to-air. Unfortunately, I think both are too similar and wish they were much more different from each other. Uair is really good, even though it doesn't launch as far as other moves, I find it rarely beaten. Fair is meh like always, though I have a high chance of connecting this after down throw.
My strategy has been mainly mixing up with charge shot and shield-jump canceling out of it to mix it up. Sometimes I just let the blast go prematurely to make others think twice about it. Because you can cancel the charge with shield, you can do several things. You can cancel into short hop (my favorite), roll (when someone is coming down on you), grab (great against people dashing at you), and spot dodge.
I feel Samus is all about maintaining certain zones where the opponent can't react and has to guess between shots, hops. and grabs. Even if the opponent has reflect, it's still a mind game, because hops and grabs beat them.
Her side tilts are great as always. Can change angle, good reach, and fairly fast. I can definitely keep up with rolls and catch people on recovery with them. Though I believe they are punishable if shielded. A couple times I've been grabbed because I couldn't time them to hit. Up tilt is still slow, but the hitbox seems pretty generous. Down tilt feels the same as well.
I feel her grab is in a good place. It doesn't feel too OP (though I have to admit, I haven't played against many Samus players, I feel like the only one).
The only thing I just don't like about Samus is her down+b bomb mechanics. She can't do anything in ball form and they made it so the explosives don't explode on contact. Now it's just reserved to altering trajectory and getting back on stage I feel. No more bomb/ball canceling missles.
Also, maybe it's just me, but her up+b special seems fairly good. Good to get out of certain combos. Also knocks people a good amount if you get the last hit compared to previous iterations. I actually killed someone with it which surprised the heck out of me.