While partly correct, the time you spend hoping to draw a proper card you could've easily been DPSing instead, guaranteeing extra DPS, rather than hoping for it. You also won't be healing in that time frame, either.
Even if the card abilities are oGCD, you still won't be able to use them at the same time as GCD abilities like SCH can with Embrace etc.
Also, it only states "Attack Speed" and "Attack Damage"; this could only mean auto-attacks rather than Skill or Spell Damage. 10% on a single target is also a very small amount, compared to the amount you could've actually added by DPSing yourself. 25% isn't bad (actually, pretty awesome) on a single-target, but again, it comes down to luck with Royal Road drawing the proper card at the perfect time.