If you find this system workable, it's a lot better than most.
1. you need your hard copies on hand.
2. you have to type a random 12-character password correctly.
3. 12 characters may not hold up against hardware-accelerated brute-force cracking for very long if the website's encrypted hash database gets compromised and they don't notice for a while. It would depend on the encryption scheme; some are very fast for a GPU-accelerated crack rack to reverse. For my most critical sites, I use as long a password as the site permits (32 characters for my bank, for example).
4. some sites allow more variety of password characteristics than others. For example, if a site only allows alpha-numeric characters, then a password of a given length wouldn't be as strong as if you can also use common symbols. And if you can use high-ANSI characters like, say, ™ or š or Ž, that further complicates a brute-force attack by expanding the character set they have to try. So you could check which sites will allow an expanded character set, and tweak your passwords to include additional stuff as permitted.
The downside is that I'm suggesting even more complication than you're already putting up with
In my case, I use a fingerprint reader and software to automate the process. One swipe, monster 32-character password entered, no errors. Unfortunately the company that makes the software got bought out, and the buyer (Apple) won't sell it anymore!