As has already been stated, nothing is fully waterproof, especially at speed. Water will get in, it's only a mater of time. If you can get your kit to keep the water out longer than your journey, then fantastic.
My normal kit is a Spada Dyno waterproof textile jacket, Rikka Hurricane textile trousers with waterproof lining, Spada Eclipse waterproof boots and Spada Enforcer waterproof gloves.
In "drizzle to normal rain" conditions, this is good for an hour, maybe an hour and a half of riding.
In heavy rain (surface flooding, that kind of heavy) the gloves last about fifteen, the boots about twenty, the trousers 25 and the jacket, maybe 45 minutes if I'm lucky?
For those days, I put on a no name one peice waterproof suit over the top. That gives me an hour on the jacket and trousers, maybe slightly longer, and the extra layer over cuffs and boot seems make them last half an hour, or there abouts each.
Pros:
One peice: no gaps to let water in
Plenty of room to slide a boot down a trouser leg, so no undressing to get it on.
Good velcro straps on the legs and good elastic around the cuffs.
Tons of hi-viz for low light rainy days
Cons:
Size: you need to order two or three sizes bigger to stop it giving you the turbo moose knuckle once it's on.
Baggy sleeves: because it's a 2XL for the length, it's baggy round the sleeves, so I have to keep some elastic straps in the bag to tuck them in so my mirrors are still useful.
It's bulky.
As a side note, you need to look after your kit. My leather gloves and boots get brush polished once a week and my waterproof kit gets treated with NikWax every three or four months.
And it doesn't matter how good your kit is, if the flood is up to your footpegs you're getting wet feet!