Assuming you're an experienced traveller, your chance to make this connection is good.

If you arrive on time, you can expect to be landside no later than 6am - and even 6.30am won't really be an issue.

Dragonair allows online checkin for PEK - https://www.seatmaestro.com/airlines...ines/check-in/

All Dragonair flights (KA), including codeshare flights operated by Cathay Pacific, departing from: Hong Kong, Bengaluru (Bangalore), Beijing, Busan, Chiang Mai, Dhaka, Guangzhou, Hangzhou, Hanoi, Kaohsiung, Kathmandu, Kolkata, Kota Kinabalu, Manila, Shanghai (Hongqiao and Pudong), Taipei, Taichung, Phuket, and Phnom Penh.

Thus, you can go straight to Gate in T3.

Bus transfer (between the Terminals) is easy and well signed

http://en.bcia.com.cn/traffic/freebus/index.shtml

After 6am, there is a bus every 10 minutes (I never found the waiting time to be longer) - head for "Gate 7 of Arrival floor of T2"

Transfer from T2 (via T1) to T3 should take no longer than 20 minutes (totally 30min including waiting, max)

That means you should get - even if you're only landside at 6.30am - be at T3 at 7am. With a boarding pass in hand, absolutely no problem (counter of Dragonair closes 60min before departure)

Of course, your incoming flight shouldn't be delayed much.. but long haul - as you noticed - rarely get delayed. And there is a little bit extra time in that schedule..

Plus, since your connecting flight isn't a long haul one, a worst-case rebooking wouldn't amount to lots of money spent.

If I had the choice, I would probably still book a longer connection, but it's doable, and your chance of making it is well above 95% in my book.