The official change list says nothing about changes to Magnet. Just the PK Fire nerf with the changes they made to it and the PKT2 nerf. It looks like DThrow took a nerf as well. I'm surprised, and a little confused. It's not as though Ness needed a nerf in this iteration (at least not that I could tell, someone correct me if I'm wrong). What could have influenced this decision? It's like it came out of nowhere.
Here's the full list. Most of it seems fairly inconsequential.
Tilts
-Forward Tilt changed to have less endlag 35 frames -> 28 frames and hit at a more horizontal angle 361 -> 34, BKB slightly reduced 12 -> 10.
Aerials
-Up Air animation edited slightly to more accurately match Melee.
Throws
-Down Throw knockback changed such that characters fly further as their percent increases. KBG 70 -> 80, BKB 85 -> 78.
Specials
-Forward Special (PK Fire)
--No longer activates on shield.
--Initial hit damage raised from 0 to 8 and now has same KB as the pillar. Victim can no longer shield between the fireball hit and the first pillar hit.
--Pillar hits changed in duration from 100 frames to 45, but time between pillar pulses is slightly reduced. Pillar pulse damage reduced from 3 to 1, but can no longer be reflected.
--Pillar gravity increased so it prevents whiffing when aerial pk fire hits some characters' heads for the first few pulses.
-Up Special (PK Thunder)
--Bolt no longer hits Shy Guys and Smashville balloon.
--Can no longer reverse ledge grab after falling from a missed PK Thunder 1
--PK Thunder 2 now always go into 20-frame landing lag instead of variable time dependent on height, but can now properly edge-cancel.
Others
-Dash Attack 3rd hit extended slightly to match Melee range.
-Spotdodge, fixed an error that had invincibility ending 1 frame earlier and having IASA 1 frame earlier than normal
-Hitlag normalized on the following attacks: Dash Attack hit2, Forward Air final hit, Up-b Startup, and PK Thunder 2.