The GT784WN is seriously inferior when compared to the Telus provided modem/gateway.
You're better off either using Telus T3200M instead. I use the T3200M when gaming online and I haven't noticed any issues.
Finding third party modems that will actually work with Telus' specific VDSL2+ implementation is extremely difficult. If you're on fibre optic, that will open up other options.
Why would you lose your internet for several hours from other people online?
Is your home internet or wifi connection unstable, or are getting kicked/banned from game servers?
So you're intermittently getting DDOSed? A VPN or anything else won't help at all for that. Your modem will still have the same IP. Depending on the gaming service being used, a VPN may not be enough to hide your IP completely either. You may want to try find some less toxic servers to game on.