Rating against CPUs is pointless...
You seem to have a handle on most of his best attributes. MK can dair gimp offstage like crazy, especially against heavies. Don't fastfall it, though. You'll typically fall at the right speed to continually hit them towards the bottom.
Utilize more upair combos. Metaknight might not be able to tornado to the ceiling anymore (thank god, so boring) but he can wrack up damage and possibly kill with an upB depending on percents and DI.
Dash attack links to nair, devastating against light to medium weight enemies. IMO, Rob is the hardest character for Metaknight to kill by far. Most heavies are easily gimped, but given Rob's almost even offstage game against Metaknight along with Meta's overall weakened kill abilities, you either have to camp you balls off and keep hitting him or be utterly ruthless and fearless offstage.
A decent Metaknight overall (against a CPU at least). Also, against humans, try using the first two hits of Meta's ftilt. Most people turn into shielding cowards when that happens, setting up for a sweet, sweet grab. Fthrow links to upB most of the time. It's the most reliable, though bad DI against his upthrow or dthrow can lead to combos.
So grab more, too.