(think about it like torrents, if your only connected to 2 seeds you wont get alot of speed)
restart client or/and try adding some supernodes.
also i hope you got bitcoin-core from bitcoin.org and no other source as theirs rumours of altcoins pretending to be the legit bitcoin client which might be another reason
No matter how many nodes you are connected to you'll only ever download from one. If you think that one is slow, close Core, delete peers.dat in the data directory and try anew. Or if you know a fast node you can use the connect= command. For example 84.200.34.113:8333. I'm sure zvs will be present shortly with some more IPs you can try.
Edit: It also depends on your hardware's capabilities how long it will take to validate the block chain.
Haha
I'll just say that it's faster connecting to 1 peer, not 20 or 30. Just choose the right peer